1 (often foll. by of, or that or lest + clause) alarmed, frightened.
2 (foll. by to + infin.) unwilling or reluctant for fear of the consequences (was afraid to go in).
Phrases and idioms:
be afraid (foll. by that + clause) colloq. admit or declare with (real or politely simulated) regret (I'm afraid there's none left).
Etymology: ME, past part. of obs. affray (v.) f. AF afrayer f. OF esfreer
Useful english dictionary. 2012.