out ‧ num ‧ ber /aʊtˈnʌmbə $ -ər/ BrE AmE verb [transitive]
[ Word Family: noun : ↑ number , ↑ numeral , ↑ numeracy , ↑ numerator , ↑ innumeracy ; adjective : ↑ innumerable , ↑ numerical , ↑ numerous , ↑ numerate ≠ ↑ innumerate ; verb : ↑ number , ↑ outnumber ; adverb : ↑ numerically ]
to be more in number than another group:
Flats outnumber houses in this area.
His troops were hopelessly outnumbered.
outnumber somebody/something by something
In nursing, women still outnumber men by four to one.
vastly/greatly/heavily outnumber
Men in prison vastly outnumber women.