IPA: /ˌɪn.sɪɡˈnɪf.ɪ.kənt/
KK: /ɪnˈsɪɡnɪfɪkənt/
Something that has little or no importance or value.
The mistake was so small that it was considered insignificant.
Insignificant is formed from "in-" (meaning not) and "significare" (meaning to signify or indicate) combined with the suffix "-ant" (indicating an agent or something that performs an action). The word means not signifying or indicating anything of importance.
Think of 'not' ('in-') signifying or indicating ('significare') anything important — that's why insignificant means something that lacks significance.