As a Verb or Adjective:
1. To be close to a particular number but not exactly that number. English = (be) about, (be) approximate.
As Modifier:
1. Used after many verbs (especially 'talk', 'write' and 'think') and before a noun to mean that the topic of the activity is the following noun. This usage is a copy of the English. English = about, concerning, pertaining to.