Here's what rhymes with insignificant.

Consider these alternatives

unimportant / important irrelevant / relevant insubstantial / sample comparatively / imperatively superfluous / thus minuscule / rule appreciable / feasible blip / it amounts / accounts fraction / action mere / will inconceivable / feasible relatively / imperatively unattractive / attractive manageable / unmanageable uncontroversial / commercial militarily / necessarily significant / insignificant immaterial / material unconnected / rejected insensitive / sensitive amount / account