https://www.myvocab.info/en-en
Following the link I found it more than familiar to me—I remember doing it several times a year or so ago with the highest score around 16,000 words.
Since then I've been reading in English more or less regularly, almost never missing the words new to me.
So now, before doing the test again, I was sure I'd add a couple of thousand points to that score but got really frustrated having finished with approximately the same score.
As long as the test-makers didn't provide correct answers, I decided to find out what is inside.
It took some time and a bit of effort, but now I can score 22,000 and more. Of course, there's nothing to be proud of--just one from many tests cracked technically to the percentage I was so far able to do.
At the same time, I do feel satisfaction having learned the words I could've never known otherwise. I hope someone may find the list useful, and by the way, in italics are the words that have really tricky pronunciation, at least to me.
abuzz - noisy like the sound of a bee
admass - (chiefly British) the segment of the public that is easily influenced by mass media
agnate - related on the father's side (syn. agnatic, paternal)
appurtenant - furnishing added support (syn. accessory, adjunct, ancillary, auxiliary)
arriviste - person who has suddenly risen to a higher economic status but has not gained social acceptance of others in that class (syn.upstart, parvenu, nouveau-riche)
bagasse - the dry dusty pulp that remains after juice is extracted from sugar cane or similar plants (syn. pulp)
bailiwick - a branch of knowledge (syn. subject area, field of study)
boscage - a growth of trees or shrubs; thick foliage; a wooded landscape (syn. thick foliage)
canticle - a hymn derived from the Bible (syn. anthem, hymn)
cantle - the back of a saddle seat (syn. backrest)
cerecloth – (archaic) a waterproof waxed cloth once used as a shroud
claudication - disability of walking due to crippling of the legs or feet (syn. lameness, limping)
condign - fitting or appropriate and deserved; used especially of punishment (syn. well-earned, deserved)
covey - a small collection of people (syn. assemblage, gathering)
curlicue - a short twisting line (syn. coil, curl)
embayment - an indentation of a shoreline larger than a cove but smaller than a gulf
enceinte - in an advanced stage of pregnancy (syn. expectant, gravid)
enjambment - the continuation of a syntactic unit from one line of verse into the next line without a pause
eponym - the name derived from a person (real or imaginary)
flibbertigibbet - a female fool
gantlet - a glove with long sleeve (also, gauntlet)
gimlet - a cocktail made of gin or vodka and lime juice
glyph - an elemental symbol within an agreed set of symbols, intended to represent a readable character for the purposes of writing (syn. grapheme, graphic symbol)
gormless - (informal) lacking intelligence and vitality
greige – 1. (of textiles) not dyed or otherwise processed 2. a gray-beige color
harridan - a scolding (even vicious) old woman (syn. nagger, scolder)
hireling - a person who works only for money
inconnu - a large edible salmonid fish, scientific name Stenodus leucichthys, with a large mouth with a protruding lower jaw and a high and pointed dorsal fin
intercalate – to insert or position between or among existing elements or layers
jonquil - widely cultivated ornamental plant native to southern Europe but naturalized elsewhere having fragrant yellow or white clustered flowers
lagniappe - a small gift (especially one given by a merchant to a customer who makes a purchase)
longueur - (art) a period of dullness or boredom (especially in a work of literature or performing art)
matelot – sailor
maunder - 1. wander aimlessly 2. talk indistinctly; usually in a low voice 3. Speak (about unimportant matters) rapidly and incessantly
meshuga - (Yiddish) senseless; crazy
mortise - a square hole made to receive a tenon and so to form a joint
mure – (archaic) wall in or imprison
niveous - snowy; resembling snow; partaking of the qualities of snow
obverse - the side of a coin or medal bearing the principal stamp or design (ant. reverse)
osier - flexible twig of a willow tree
paraclete - an advocate; one called to aid or support; hence, the Consoler, Comforter, or Intercessor; - a term applied to the Holy Spirit
prehensile - immoderately desirous of acquiring e.g. wealth (greedy, avaricious, covetous)
quatorze - the four aces, kings, queens, knaves, or tens, in the game of piquet (so called because quatorze counts as fourteen points)
razzamatazz - any showy or exciting display (razzle-dazzle)
ream - a quantity of paper; 480 or 500 sheets; one ream equals 20 quires (one quire is 24 or 25 sheets)
rebarbative - serving or tending to repel (syn. repellent)
recherche - lavishly elegant and refined ( syn. exquisite)
recusant – 1. (of Catholics) refusing to attend services of the Church of England (syn. nonconformist)
2. refusing to submit to authority (syn. dessentient)
renascent - rising again as to new life and vigor (resurgent)
riparian - of or relating to or located on the banks of a river or stream
sacerdotal - associated with the priesthood or priests (hieratic, priestly)
serried - especially of rows as of troops or mountains) pressed together (compact)
spicule - small pointed structure serving as a skeletal element in various marine and freshwater invertebrates e.g. sponges and corals
suasive - having power to persuade; persuasive
syllabub (sillabab) - spiced hot milk with rum or wine
tabard - a short sleeveless outer tunic emblazoned with a coat of arms; worn by a knight over his armor or by a herald
theorbo - an instrument made like large lute, but having two necks, with two sets of pegs, the lower set holding the strings governed by frets, while to the upper set were attached the long bass strings used as open notes
titivate - make neat, smart, or trim
treacle - a pale cane syrup (fig. writing or music that is excessively sweet and sentimental)
truant - absent without permission
wheedle - influence or urge by gentle urging, caressing, or flattering
whirligig - A large, rotating machine with seats for children to ride on for amusement (merry-go-round, roundabout)
zounds – (archaic) an exclamation formerly used as an oath, and an expression of anger or wonder