несъвършен означава в английски

deficient▼(lacking something essential)
adjective
[UK: dɪ.ˈfɪʃnt] [US: də.ˈfɪ.ʃənt]

imperfect▼(not perfect)
adjective
[UK: ɪm.ˈpɜː.fɪkt] [US: ˌɪm.ˈpɝː.fɪkt]

imperfection [imperfections]▼(state of being imperfect)
noun
[UK: ˌɪm.pə.ˈfek.ʃn̩] [US: ˌɪm.pər.ˈfek.ʃn̩]