so as to precede something in order of time <call ahead for reservations>
Phrases in advance
toward a point ahead in space or time <sent me ahead to get a place in the check-out line while she went to get the eggs and milk>
toward or at a point lying in advance in space or time <the line moved ahead at a snail's pace>
Seen & Heard
What made you want to look up ahead? Please tell us where you read or heard it (including the quote, if possible).