This is the verse translation, not a definition of the individual word.
O you who believe, when you go to fight in the way of Allah, make sure [who you fight]; and do not say to someone who offers you the greetings of peace, “You are not a believer”[1] – seeking gains of the life of this world, while Allah has abundant gains. You were in the same position before, then Allah blessed you [with Islam]. Therefore make sure, for Allah is All-Aware of what you do.
Source
[1] This is someone who withholds from fighting and declares that he is a believer.