Rooster

Rooster is more often used in American English than in British. It is used as a euphemism for what is properly a cock, an adult male bird of the domestic fowl Gallus domesticus - as this word is used informally to mean 'penis', a usage which is felt by some people to be tabu. That should not stop you using the word entirely correctly, in formal English, for its accurate meaning in ornithology, agriculture and biology generally. See also cockerel.