hau whakapipi
1. (noun) air mass.
Ina tūtaki te hau whakapipi mahana me te hau whakapipi mātao, ka tōtā te wairehu o roto i te hau takiwā mahana, ā, ka puta te ua. Ka kīia he ua arotuki tēnei momo ua (RP 2009:422). / When warm and cold air masses meet the water vapour in the warm air condenses and rain appears. This type of rain is called frontal rain.