Boulder rhymes with:
bolder, beholder, bolder, colder, dolder, folder, golder, holder, molder, moulder, nolder, older, polder, shoulder, smolder
Boulder sounds like:
balder, baldor, baldree, baldry, baldur, balladur, balter, baltierra, beholder, beladur, bellwether, belter, bewilder, billeter, billiter, bladder, blather, blatter, bloodier, blotter, blowdry, blowdryer, boelter, bolder, bollettieri, bolter, boulter, builder