It is an optimistic question, but the infinite English language has given us technical terms for all sorts of strange noises emanating from the body by design and otherwise.

Well, I'd have to hear how you pronounce it, but the way I do I'd transcribe as /pft/ (or more narrowly [pft̚]) in IPA and if I had to tell somebody what that transcription was, I'd use: a voiceless bilabial-labiodental affricate which transitions into a voiceless unreleased alveolar stop.

Ceci n'est pas un seing.