The action of one who drops in.

present participle of drop in

plural of dropful

A single drop (of a liquid).

plural of dropping in

Third-person singular simple present indicative form of drop by

(US) A letter mailed at a post office and either kept for general delivery, or delivered to a post office box, at that same post office.

one who dropkicks.

A sudden downward slope. / The precipitous outer side of a coral reef, facing the open sea. / A sudden decrease. / A delivery; the act of leaving a package, etc.

(rugby union, rugby league) A goal scored by kicking the ball through the goal from open play, after the ball has touched the ground.