n. (pl. -ies) 1 courteous behaviour; good manners. 2 a courteous act. 3 archaic = CURTSY. by courtesy by favour, not by right. by courtesy of with the formal permission of (a person etc.). courtesy light a light in a car that is switched on by opening a door. courtesy title a title held by courtesy, usu. having no legal validity, e.g. a title given to the heir of a duke etc.
[ ME f. OF curtesie, co(u)rtesie f. curteis etc. COURTEOUS ]