To act mature, to act as a 21 year old.
" Stop being immmture, you got to be 21 about it."
by jkk April 4, 2006
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To own up to or acknowledge and accept responsibility for actions and/or wrongdoings regardless of the repercussions and opinions of others
" I already know you lying so Be 21 about it."
by URBANEDUCATEDREDNECK December 17, 2015
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