Having a very thin neck. / (idiomatic, US, derogatory) Insubstantial; weak.

(informal) A person with a very thin neck. / (idiomatic, US, derogatory) An insubstantial person; a weakling.

(idiomatic) To take a risk, putting oneself in a vulnerable position.

(astronomy) A type of nebula that does not emit or reflect (visible) light, and thus obscures light sources behind it.

(astronomy) A nebulosity surrounding a dying red giant, consisting of material expelled by the star.

(astronomy) A nebula that consists of dust which reflects starlight and appears blue in photographs.

(meteorology, astronomy) The characteristic of being nebulous; cloudiness (measured in octas).

a miss which was nearly a hit or collision / (by extension) a scenario which ends safely but might well have ended in disaster

To convert liquid into a fine spray of aerosols, by using a nebulizer; to atomize / (medicine) To treat a patient with medicine applied using a nebulizer

(logic) A statement Q in relation to statement P such that P implies Q.