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