¦ ordinal number
1. coming before all others in time or order; earliest; 1st.
before doing something else.
2. foremost in position, rank, or importance.
Brit. a place in the top grade in an examination for a degree.
3. for the first time.
informal something never previously occurring or done.
4. with a specified part or person in a leading position: the car plunged nose first into the river.
5. Music performing the highest or chief of two or more parts for the same instrument or voice.
Phrases
at first at the beginning.
first and foremost more than anything else.
first and last fundamentally.
first of all before doing anything else.
?most importantly.
first off informal as a first point; firstly.
first past the post winning a race by being the first to reach the finishing line.
?Brit. denoting an electoral system in which a candidate or party is selected by achievement of a simple majority.
first thing early in the morning; before anything else.
first up informal first of all.
in the first place as the first consideration or point.
?to begin with.
of the first order (or magnitude) excellent or considerable of its kind.
Origin
OE fyr(e)st; of Gmc origin.