Immovable rhymes with:
removable, movable, removable, approvable, movable, provable, removable, achievable, approvable, believable, conceivable, drivable, forgivable, inconceivable, livable, lovable, microwavable, movable, observable, provable, receivable, removable, solvable, survivable, unbelievable, unforgivable, unlivable, unsolvable
Immovable sounds like:
immobile, impala, impale, impel, imply, ineffable, inflow