(intransitive) To become ill, to fall ill.

(idiomatic, usually with of) A weak member of a peer group, especially the weakest.

Indicates that the speaker has an illness.

(slang, drugs) Sick due to withdrawal from opiates; in withdrawal.

plural of sick man

(US, military) A daily lineup of military personnel requiring medical attention.

plural of sick call

(idiomatic, informal) A list of people who are ill

(informal, transitive, intransitive) To vomit.

(UK) A note from a doctor certifying the patient is ill, and therefore unable to go to work, school etc. / (UK, idiomatic) Someone who dodges work because of (feigned) illness.