out(side) of wedlock
Without being married to the other person in question. I know my grandparents raised their eyebrows when my girlfriend and I had our son out of wedlock, but they've never been rude about it. Back in my day, it was pretty unheard of to even live with someone outside of wedlock.
out of wedlock
Of parents not legally married, as in Over the centuries many royal children were born out of wedlock. The noun wedlock, for the state of being married, is rarely heard today except in this phrase, first recorded in 1675; its converse, in wedlock, dates from the 1300s and is even more rarely used.
out of wedlock
Of parents not legally married to each other: born out of wedlock.