oo-

1. An unfertilized female reproductive cell in algae and fungi.
2. A large non-motile female gamete or egg cell, formed in an oogonium and ready for fertilization.

Oogonium is a female reproductive structure in certain thallophytes (algae, fungi, and lichens), usually a rounded cell or sac containing one or more oospheres.

A type of egg mass made by any member of a variety of species (usually insects or mollusks).

A gravid (pregnant) female praying mantis will produce a large foam mass, called an ootheca. This ootheca can contain up to 300 eggs, all protected in the foam sack. These oothecae can take up to five months to hatch, some species hatching in shorter intervals. Hatching can take up to five weeks for all of the nymphs to fully emerge.

The part of the oviduct of certain trematode (parasitic) worms in which the ova are completed and furnished with a shell.