a matter of life and (also or) death: something on which the life or death of a person depends; (also in extended use) a matter of vital…

a test question, one endangering one's ‘neck’.

Nautical. An act or instance of lightly or briefly striking rocks, the seabed, or another vessel without stopping or losing speed; (later also more…

(intransitive) to perform on the tightrope; transitive to walk along as if on a tightrope.

(a) the edge of a razor; a very sharp edge; (figurative) a narrow foothold, a critical or precarious situation (cf. on the (or a) razor's edge at…

In immaterial sense. shaky do, a difficult or risky situation, a close shave. slang (originally R.A.F. slang).