To go out onto the playing field. / To begin military operations. / (horse racing) To stake one's money against the favourite, taking the chances of the field against the chance of one horse.

(idiomatic) To discourage someone greatly; to cause someone to lose hope or the will to continue; to thwart or minimize someone's ambitions.

(games) A children's game similar to hide and seek, with the addition of a target such as a flag.

To be joking, but at the same time really mean it.

Short for a bird in the hand is worth two in the bush.

(law, archaic) The party to a legal dispute against whom a complaint was initially raised in a court.

(chiefly US, idiomatic) Done by feel, guess, or trial and error rather than by careful planning, thought or technique.

(law, archaic) The party to a legal dispute who first raised a complaint in a court. / (law, archaic) The first party named in a contract, generally the party agreeing to perform a duty thereunder.

(UK, idiomatic, humorous) Expresses disbelief.

Not yet hardened into bone or strengthened into sinew. / Young, weak, and unformed.