shirt·sleeve / ˈshərtˌslēv/ • n. (usu. shirtsleeves) the sleeve of a shirt: he rolled up his shirtsleeves. • adj. 1. (of weather) warm enough to wear a shirt with no jacket: the shirtsleeve November days before the hard cold set in. 2. (of work or an atmosphere) straightforward and unpretentious, with hard work being done: thousands have used this shirtsleeve workshop to improve their company profits. PHRASES: in (one's) shirtsleeves wearing a shirt with nothing over it.DERIVATIVES: shirt·sleeved adj.