In secrecy or in hiding. / (horse-racing) Of a horse: restrained from performing at its best in a race, so as to mislead others regarding its potential.

(idiomatic) Without attracting notice; in an undetected or secretive manner.

(idiomatic) In operation, in progress, commenced. / (nautical, of a vessel) moving through the water; not anchored, moored, aground, or beached. / Into motion, into its course.

Subjected to enemy attack with firearms. / (figuratively) Criticized or held responsible for something.

Arrested by the police.

(idiomatic) Whose future is uncertain due to an anticipated threat or change in circumstance. / (idiomatic) Under suspicion; subject to critical inspection.

(idiomatic) In Australia. / (idiomatic) Into Australia; to Australia. / (euphemistic, rare) Hell; in Hell.

(idiomatic) Intoxicated, inebriated, or otherwise stupefied by an ingested mind-altering substance, typically alcohol; drunk.

(idiomatic) Under close scrutiny or examination.

(idiomatic) Under great pressure to perform. / (poker) Of, pertaining to, or in the situation of first player to act on the first round of betting.