shirtsleeves The state of wearing no coat, jacket, or other outer garment over one's shirt: dined in shirtsleeves; balmy weather that had them down to their shirtsleeves.
adjective
also shirt·sleeved(-slēvdˌ) Dressed without a coat: shirtsleeve spectators; a shirtsleeved orchestra.
also shirtsleeves Calling for the removal of a coat or jacket; not requiring a coat or jacket for comfort: shirtsleeve weather; a shirtsleeves picnic.
also shirtsleeves Marked by informality or straightforwardness: shirtsleeve politics; a shirtsleeves conference.