N plus the '@' sign equal the nick name for a girl with the first three letters N-A-T in her name. Such as:
"Hey N@, how have you been?"
A Pittsburgh phrase meaning "and that." Also spelled and pronounced "n'at." Part of the dialect of English known as Pittsburghese.
"Hey Joe, you goin dahn tuh Wholly's tuh get some sawsage n@?"
"No, I'm going dahn tuh Primanti Bros tuh get some sammiches n@."