ballon d'essai

[ba-lawn de-se] /ba lɔ̃ dɛˈsɛ/
noun, plural ballons d'essai
[ba-lawn de-se] /ba lɔ̃ dɛˈsɛ/ (Show IPA).
French.
1.
trial balloon (def 1).
British Dictionary definitions for ballon d'essai

ballon d'essai

/bæˈlõ dɛˈseɪ/
noun (pl) ballons d'essai (bæˈlõ dɛˈseɪ)
1.
a project or policy put forward experimentally to gauge reactions to it Compare trial balloon
Word Origin
C19: from French, literally: trial balloon