незабавен означава в английски

immediate▼(without delay)
adjective
[UK: ɪ.ˈmiː.dɪət] [US: ˌɪ.ˈmiː.diət]

instant▼(imminent)
adjective
[UK: ˈɪn.stənt] [US: ˈɪn.stənt]

instantaneous▼(occurring, arising, or functioning without any delay; happening within an imperceptibly brief period of time)
adjective
[UK: ˌɪn.stən.ˈteɪ.nɪəs] [US: ˌɪn.stən.ˈtæ.niəs]

speedy [speedier, speediest]▼(characterized by rapid or swift motion)
adjective
[UK: ˈspiː.di] [US: ˈspiː.di]