Main Entry: com·plain

Pronunciation: \kəm-ˈplān\

Function: intransitive verb

Etymology: Middle English compleynen, from Anglo-French compleindre, from Vulgar Latin *complangere, from Latin com- + plangere to lament — more at plaint

Date: 14th century

1 : to express grief, pain, or discontent <complaining about the weather>
2 : to make a formal accusation or charge

— com·plain·er noun

— com·plain·ing·ly \-ˈplā-niŋ-lē\ adverb