What does philippic mean?

A philippic is a bitter verbal attack, especially if it denounces or condemns someone or something; a harangue, or a serious scolding.

In Jane Austen's Sense and Sensibility, party guests are admiring Elinor's artwork when she suddenly receives unfair comparison to a stranger named Miss Morton. Marianne jumps in to defend her sister:

"This is admiration of a very particular kind! — what is Miss Morton to us? — who knows, or who cares, for her? — it is Elinor of whom WE think and speak." . . .

Mrs. Ferrars looked exceedingly angry, and drawing herself up more stiffly than ever, pronounced in retort this bitter philippic, "Miss Morton is Lord Morton's daughter."