- propolisAn aromatic glue-like substance produced by honeybees from tree resin, waxes, and their own secretions, used in the construction of their hives.
- proemptosisThe addition of a leap day to the lunar calendar.
- proostracumThe anterior prolongation of the guard of the phragmocone of belemnites and allied fossil cephalopods, whether horny or calcareous.
- propterygiumThe anterior of three principal cartilages in the fins of some fishes.
- proscolexAn early larval form of a trematode worm; a redia.
- prozeugmaA zeugma where the governing word occurs in the first clause of the sentence.