Gigantic rhymes with:
antic, atlantic, bankatlantic, frantic, midlantic, pedantic, romantic, semantic, sycophantic, transatlantic
Gigantic sounds like:
gamunde's, gandhi's, gannett's, gantos, gantz, genentech, genentech's, genetic, genetics, gent's, gentz, giaconda's, giannattasio, giant's, giants, giants', gintz, gnats, gonads, gondek, guandjo, guandjo's, gundog, gwyneth's, gwyneths