неубедителен означава в английски

inconclusive▼(not leading to a conclusion)
adjective
[UK: ˌɪnk.ən.ˈkluː.sɪv] [US: ˌɪnk.ən.ˈkluː.sɪv]

lame [lamer, lamest]▼(slang: unconvincing)
adjective
[UK: leɪm] [US: ˈleɪm]

unconvincing▼(not convincing)
adjective
[UK: ˌʌnk.ən.ˈvɪns.ɪŋ] [US: ˌʌnk.ən.ˈvɪns.ɪŋ]