■ preposition & adverb
1》 [as preposition ] on the subject of; concerning.
2》 used to indicate movement within a particular area or location in a particular place.
3》 [as adverb ] approximately.
Phrases
be ~ to be on the point of.
know what one is ~ informal be sensible and self-possessed.
Origin
OE onbūtan , from on 'in, on' + būtan 'outside of' (see but 2 ).