Here's what rhymes with caustify.
high thy vi hi shy sigh fi hy thigh vie psi hai cy fy sy thei phi by my why die lie y buy fly sky guy justify tie bi bye chi defy dye nigh pi pie spy thai certify dei fry ly quae rye sly ty wir awry lye mai muy nai wry kai lai luy mei tai wai edify sty bonsai deify ossify stye turfy slier apply dry try cry deny satisfy modify specify classify testify verify gratify notify ply underlie amplify pacify pry ratify tri trie belie pri terrify typify untie codify acidify aquae firefly mystify spry amebae calcify horrify stupefy lanai scurfy versify shanghai vitrify speechify banzais dandify supply thereby occupy rely clarify hereby qualify alkali signify simplify butterfly glorify purify quantify alibi fortify magnify nullify rectify unify decry falsify pupae solidify amoebae crucify descry dignify mollify mortify overlie ramify vilify stratify stultify ultrahigh vivify blowfly petrify overfly scarify barfly mummify prettify beatify overbuy yuppify identify reply imply nearby stimuli whereby comply multiply goodbye alveoli diversify samurai standby beautify lullaby termini liquefy personify demystify retry triply emulsify reunify dissatisfy liquify declassify hyperbolae drachmai refortify ripply syllabify nuclei exemplify intensify indemnify objectify oversupply resupply detoxify dragonfly electrify misapply reclassify revivify gentrify solemnify disqualify preoccupy cumuli misidentify oversimplify transmogrify