1 courteous behaviour; good manners.
2 a courteous act.
3 archaic = CURTSY.
Phrases and idioms:
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.
Etymology: ME f. OF curtesie, co(u)rtesie f. curteis etc. COURTEOUS
Useful english dictionary. 2012.