Princi-pal.
1. (Carpentry.) An important timber in a frame, as a principal beam. A principal rafter, one of the heavy rafters which support the purlias and common rafters. A principal brace, one immediately under the principal rafter. A principal post, the corner post of a frame.
2. (Music.) A stop of an organ an octave higher than open diapason and in unison with flute. It is the first or medium stop which is tuned, all the other stops being tuned from it. See stop.