under the arm—
1. held between the arm and the body:
- The hat could be worn or carried under the arm at all times except in the presence of the King.
2. (sl.) inferior; of poor quality:
- I read no matter how bad the book and some are right under the arm.
under-arm—(attrib.)
1. that can be carried “under the arm”:
- Whatever she carries about with her she keeps in an “underarm bag.”
2. (sl.) pornographic; obscene:
- One of the first things Randle asked him was did he make any under-arm films.