From Longman Dictionary of Contemporary Englishrubber bootˈrubber boot noun [countable] 
DHHDCC American English a tall boot made of rubber that keeps your feet and the lower part of your legs dry SYN wellington boot British English
DHHDCC American English a tall boot made of rubber that keeps your feet and the lower part of your legs dry SYN wellington boot British EnglishExamples from the Corpus
rubber boot• The rubber boot is to stop ingress of dirt, etc. into the splines, causing premature failure. 