There are two questions here:
- (Terminology) Is making a bid over an opponent still called an overcall if your partner has already bid?
There are two competing uses (from Merriam-Webster):
Definition of overcall
: to make a higher bid than (the previous bid or bidder) in a card game
: to bid over an opponent's bid in bridge when one's partner has not bid or doubled
The first sounds a bit old fashioned, and the second is what I'd expect in modern bridge books, which tend to (cf. this lesson by Larry Cohen) use the names:
West, Partner (Opener): 1 Club
North, TD (Overcaller): 1 Spade
East, You (Responder): 2 Hearts
South (Advancer): [to call]
- Did your partner need to alert your bid, regardless of terminology?
No, at least not in the American Contract Bridge League. See the Alert Procedures:
Definition of expected length for natural bids for the Alert Procedure
Three or more in a minor suit
(Also: An opening bid of 1♣ is natural if, by agreement, it may be exactly
4=4=3=2 with two clubs, three diamonds, and four cards in each major.)
Four or more in a major for opening bids, rebids and responses
Four or more for an overcall at the one level, five or more for higher levels
Five or more for a weak two-bid
Six or more for a weak three-bid
Side Note: It doesn't matter to the result, but I couldn't find the definition of overcall that the ACBL Alert Procedures are using. I would expect from experience that it is the second one.