(idiomatic) A quiet, non-participating, or unseen observer; an eavesdropper or witness.

(idiomatic) To go ahead; to do as one pleases.

(idiomatic) Slyly, in an inconspicuous manner, so as not to be seen; secretly; stealthily.

(informal) To speak about things rashly or foolishly, when it would be better to stay silent.

(transitive, simile) To be intimately knowledgeable about something.

To drink alcohol heavily to deal with miserable feelings

(idiomatic) No harm to one.

(US, colloquial) murder in the first degree.

(idiomatic) To be absolutely sure of something; to be certain enough of something to wager everything.

(idiomatic) Hidden, in reserve.