When a white pawn and a black pawn are touching on a file, what is it called?
I think what you're asking about is referred to as a "blocked pawn". There is another question here that asks basically the same question, except in reverse... A pawn can also be blocked by another of the opponent's pieces, rather than another pawn. In either case, it can't make any progress unless the pawn/piece blocking it somehow goes away, or unless an opportunity arises for it to capture on an adjacent file.
With the exception of Hans Kmoch's attempt to give it a name, which never caught on (I have never seen anyone else use it anywhere), they really do not have a name that I have even seen.
I probably have seen this referred to mostly as "two opposing pawns", but that is really just English rather than a specific chess term.
According to this post, pawns that block each other are called a "ram".
For the scenario where one pawn is on the second rank and the other is its sixth rank but cannot be captured by a pawn on an adjacent file, YouTube vlogger Kingscrusher coined the term "thorn pawn". The chess engine Leela Zero seems to establish thorn pawns quite frequently as part of its strategy, and they can be amazingly effective at limiting enemy mobility. If e.g. Black has castled kingside and the king is at g8, a thorn pawn at g6 can make it impossible for Black to establish f7, g7, or h7 as escape squares. If White keeps a rook ready to pounce on the eighth rank, Black will have to keep a rook on the eighth rank. Unless or until Black can resolve that situation, White's thorn pawn will enormously upgrade the playing strength of White's rooks and downgrade the playing strength of Black's.