Estimation rhymes with:
automation, intimation, acclamation, acclimation, amalgamation, animation, approximation, automation, consummation, defamation, exclamation, inflammation, intimation, proclamation, reclamation, summation
automation, intimation, acclamation, acclimation, amalgamation, animation, approximation, automation, consummation, defamation, exclamation, inflammation, intimation, proclamation, reclamation, summation