big, considerable, huge, large, massive
marked, noticeable, significant, substantial
dramatic, drastic, precipitous, rapid, severe, sharp, sudden
slight, small
steady
pressure, price, temperature
A sudden temperature drop could lead to a new ice age.

experience, suffer
The restaurant has suffered a big drop in trade.

cause, lead to

drop in
The glut of coffee led to a sharp drop in prices.

precipitous, sheer, steep, vertical
The cliff plunged in a sheer drop down to the beach.

long

single
We mustn't waste a single drop.

tiny
Tiny drops of sweat appeared on her forehead.

tear (usually teardrop)
dew, rain (usually dewdrop, raindrop)

wipe, wipe off
She wiped a drop of water from her chin.

fall
Great drops of rain started to fall.

roll down sth

drop of
Large drops of sweat rolled down her face.

accidentally
carelessly, casually
He casually drops the latest buzzwords into the conversation.

almost, nearly
instantly, promptly
He saw Emma and promptly dropped his tray of drinks.

in, into, on, onto
I accidentally dropped my glasses into the water.

heavily
gently, lightly
immediately, instantly, quickly
slowly
He slowly dropped to the floor.

limply
His arms dropped limply to his sides.

down, open
Her mouth dropped open in disbelief.

let sth
She smiled and let her eyes drop again.

be ready to
I'm ready to drop (= because I am so tired).

into, onto, to
The cheese drops onto a conveyor underneath.

drop like a stone (figurative)
Her heart dropped like a stone at this news.

considerably, dramatically, drastically, significantly, substantially
The price of oil has dropped significantly.

fast, rapidly
abruptly, precipitously, sharply, suddenly
steadily
slightly
further

be likely to, be unlikely to
Sales are likely to drop further.

below
The temperature rarely drops below 40°.

by
The price has dropped by 15%.

from, to
The number of children in the class has dropped from 25 to 18.

sharply, steeply
away

into, to, towards/toward
The land dropped steeply away into a small valley.

quietly
unceremoniously
She was unceremoniously dropped by her record label.

from
He has been quietly dropped from the England team.

in favour/favor of

quietly
The subject was quietly dropped.

immediately, quickly, suddenly
He suddenly dropped his habitual banter.

eventually, finally
altogether
When nobody volunteered, the idea was finally dropped altogether.

let sth
Can't we just let the matter drop?

agree to, decide to
Both countries have agreed to drop border controls.

in favour/favor of
The formal grade of Geologist was dropped in favour/favor of Scientific Officer.

Drop is used with these nouns as the subject:
arm, attendance, barometer, breeze, count, export, eye, face, hand, head, helicopter, humidity, import, income, index, jaw, leaf, level, mouth, number, percentage, price, productivity, profit, rate, rating, revenue, sale, shoulder, standard, stock, sun, takings, tear, temperature, turnover, usage, voice, weight, wind, yield

Drop is used with these nouns as the object:
accent, acid, anchor, appeal, backpack, bag, ball, baton, bomb, bombshell, briefcase, case, catch, ceiling, charade, charge, claim, class, clutch, crumb, flare, formality, gaze, gun, head, hint, insistence, jaw, kiss, leaflet, litter, load, matter, name, needle, objection, opposition, pants, pass, per cent, plan, point, pretence, price, proposal, receiver, reference, sail, shoulder, stipulation, stitch, subject, suit, suitcase, torpedo, tray, trousers, voice, weapon, wrapper