Definition of oat
1 a
: any of several grasses (genus Avena);
especially
: a widely cultivated cereal grass (A. sativa)
b
: a crop or plot of the oat;
also
: the seed of an oat
—usually used in pl. but singular or plural in construction
2
archaic
: a reed instrument made of an oat straw
—
feel one's oats
: to act in a newly self-confident and often self-important manner
