(pharmacology) A dose of liquid medicine in the form of a drop (sense 1). / (pharmacology, chiefly in the plural) A liquid medicine that is intended to be administered in drops (sense 1).

(intransitive) Of a liquid: to fall in drops or droplets. / (intransitive, also figuratively) To fall (straight down) under the influence of gravity, like a drop of liquid.

Provided for short-term use. / (manufacturing) Fit to substitute for some element in a complex system without changes to the existing infrastructure.

One who casually drops in (visits unannounced or without appointment). / An informal event that does not require booking in advance. / A place that can be visited casually, without an appointment.

(colloquial) To visit informally and spontaneously.

(idiomatic) To arrive casually and unannounced, with little or no warning; also, to visit without an appointment. / (surfing) To paddle into and take off on a wave another surfer is already riding.

Alternative spelling of drop-in.

A brief visit, especially (politics) for the purpose of attracting voters or motivating one's staff.

(video games) A style of competitive or cooperative multiplayer game where players can join or leave a game at any time without incurring a penalty for themselves or other players.

plural of dropping in