on the subject of; concerning

I was thinking about you

a book about ancient Greece

it's all about having fun

used to indicate movement within a particular area

she looked about the room

used to express location in a particular place

rugs were strewn about the hall

he produced a knife from somewhere about his person

used to indicate movement within an area

men were floundering about

finding my way about

used to express location in a particular place

there was a lot of flu about

(used with a number or quantity) approximately

reduced by about 5 per cent

he's about 35