(simile) Incredibly thin, at an unhealthy-looking level of thinness.

(idiomatic) dangerously, hazardously, delicately

(idiomatic) In a dangerous, hazardous, or delicate situation; at risk.

(finance, stock market) The characteristic of lower trading frequency, commonly observed with lesser known companies and firms listed on the market. It often suggests higher level of investment opportunity and risk for investors, less transparency and less public information.

(idiomatic) Immediately and inexplicably out of sight.

scarce, or difficult to find.

(idiomatic) Overly sensitive to criticism; quick to take offence; irritable; touchy / Used other than figuratively or idiomatically: see thin, skinned.

Very thin, as thin as a wafer. / Extremely marginal or tenuous.

(transitive) To make sparse; to remove some of a group of newly-planted plants in order to allow the remaining ones to grow unimpeded / (intransitive) To become sparse.

Both thickets and thin woodland; (through) all obstacles in a path. / (idiomatic) Both good and bad times.