late 14c., "an overseer, guardian, steward," from Latin actor "an agent or doer," also "theatrical player," from past participle stem of agere (see act (n.)). Mid-15c. as "a doer, maker," also "a plaintiff." Sense of "one who performs in plays" is 1580s, originally applied to both men and women.
An athlete who is good at pretending he has been hurt or fouled; esp, a baseball player who very convincingly mimes the pain of being hit by a pitch