What is the meaning of Oat?

Widely cultivated cereal grass, typically Avena sativa.

Any of the numerous species, varieties, or cultivars of any of several similar grain plants in genus Avena.

The seeds of the oat, a grain, harvested as a food crop.

A simple musical pipe made of oat-straw.

The tiniest amount; a whit or jot.

nominative plural of oka

Source: wiktionary.org