trial balloon

Meanings

1. A small balloon released into the sky to determine the direction and tendency of winds in the upper air before a manned ascent in a larger balloon; a ballon d'essai.
2. An idea, suggestion, or prospective action, product, etc., offered to an audience or group in order to test whether it generates acceptance or interest.

Etymology

Calque of French ballon d’essai (“small balloon released into the sky to determine the direction and tendency of winds in the upper air before a manned ascent in a larger balloon; (figuratively) prospective action to test acceptance”): ballon (“balloon”), essai (“trial, try; assay”).