Home › Words › U › undercolourundercolourundercolour means A colour used as a base and then coloured over, as in watercolour painting.EtymologyFrom under- + colour.nounA colour used as a base and then coloured over, as in watercolour painting.The colour of the underparts of a bird, rabbit, etc.verbTo colour insufficiently.Definitions & examples from Wiktionary (CC BY-SA 3.0).