Meaning of “drop” - Learner’s Dictionary

drop

noun uk us /drɒp/
LIQUID [ C ]

B1 a small, round-shaped amount of liquid:

I felt a few drops of rain.
REDUCTION [ no plural ]

B2 a reduction in the level or amount of something:

There has been a drop in crime recently.
SMALL AMOUNT [ no plural ]

a small amount of a liquid you can drink:

Would you like a drop more milk?
DISTANCE [ no plural ]

a vertical distance down from somewhere to the ground:

It's a drop of about 50 metres from the top of the cliff.

(Definition of “drop noun” from the Cambridge Learner’s Dictionary © Cambridge University Press)