(idiomatic) To sign one's name on a list when entering a place, to indicate one's arrival. / (computing) To take some action to access a secured program or web page on a computer; to log in.

To rely on a single source (as of income), rather than diversifying.

(idiomatic) Explicitly, in writing, clearly and without doubt or misunderstanding, without any grey areas. / (literally) Using shades of gray rather than color.

(idiomatic) To act against one's own interests; to unintentionally behave self-destructively.

(idiomatic, intransitive) To be crazy or eccentric.

(idiomatic) To create a difficult situation whose unpleasant consequences one must now endure.

(idiomatic) At no time whatsoever.

Comprehensive, thorough, detailed.

(idiomatic) In large quantities; to a high degree; to excess, without restraint. / (idiomatic) Beyond doubt.

(idiomatic, UK) To introduce a problem, dilemma or obstacle, something unexpected or troublesome.