Downtime rhymes with:
centime, funtime, meantime, noontime, airtime, alltime, anytime, bedtime, centime, christmastime, daytime, dinnertime, everytime, flextime, fulltime, funtime, halftime, lifetime, longtime, lunchtime, maritime, mealtime, meantime, movietime, nighttime, noontime, overtime, parttime, pastime, peacetime, primetime, quicktime, ragtime, schooltime, showtime, sometime, springtime, summertime, wartime, wintertime
Downtime sounds like:
damnation, dandeneau, dantin, danton, dantoni, dantonio, dantuono, demotion, denden, denomination, dentin, dentine, dentino, dentition, denton, dentton, detention, detonation, diantonio, diminution, dimunition, domination, donathan, donation, downtown, dundon, dunedin, dunton