Definitions for old lady
Random House Webster's College Dictionary
one's girlfriend or female lover.
Category: Common Vocabulary, Sexuality
Origin of old lady:
your own wife
"meet my old lady"
An elderly woman.
One's girlfriend, wife or significant other.
The Bank of England, sometimes referred to as the "Old Lady of Threadneedle Street" or simply "The Old Lady". (see: Bank of England on Wikipedia)