keep your shirt on

: to retain in one's possession or power

: to refrain from granting, giving, or allowing

: to have in control

: the means or provisions by which one is kept

: one that keeps or protects: such as

: fortress, castle

: of or relating to you or yourself or yourselves especially as possessor or possessors, agent or agents, or object or objects of an action

: of or relating to one or oneself

used with little or no meaning almost as an equivalent to the definite article the

: a garment for the upper part of the body: such as

: a cloth garment usually having a collar, sleeves, a front opening, and a tail long enough to be tucked inside trousers or a skirt

: undershirt