(British English) (North American English mom) (informal) a mother My mum says I can't go. Happy Birthday, Mum. A lot of mums and dads have the same worries. See related entries: Relations Word Originnoun mid 17th cent.: abbreviation of mummy ‘mother’.Extra examples The cat acted as a surrogate mum to the chicks. The group is aimed at new mums with young babies. My mum says I can’t go.