Interrogation \In*ter`ro*ga"tion\, n. [L. interrogatio: cf. F. interrogation.]

1. The act of interrogating or questioning; examination by questions; inquiry.

2. A question put; an inquiry.

3. A point, mark, or sign, thus [?], indicating that the sentence with which it is connected is a question. It is used to express doubt, or to mark a query. Called also interrogation point.

Source: Webster's Revised Unabridged Dictionary (1913)