unconvincing
1. [ adjective ] not convincing
Examples:

"unconvincing excuses" "as unconvincing as a forced smile"

Related terms: convincing unpersuasive incredible
2. [ adjective ] having a probability to low to inspire belief
Synonyms: unbelievable unlikely improbable
Related terms: implausible
Similar spelling:   unconvincingly
  unconvinced
  unconcern
  unconventional
  unconnected
  uncongenial
  unconfirmed
  unconfident
  unconscientious
  unconsidered