To behave in a manner appropriate to one's age. / (imperative, originally US) To behave in a mature manner; to avoid being childish.

In a pleasing state or form.

(idiomatic) Close behind; pursuing or following closely.

(bingo) eight

(informal) Legitimate; honest; upright.

Used other than figuratively or idiomatically: see let, on. / (idiomatic) to reveal or indicate, especially unintentionally or against one's wishes

(idiomatic) barely; closely; by a narrow margin; with nothing to spare.

The state of having invested heavily in just one area. / The state of having devoted all of one’s resources to one thing.

(idiomatic) To relax.

(idiomatic) Praise, congratulations.