In chess, a "Tal move" is an informal designation for a move that looks extremely bad at first glance, and possibly even technically is a blunder according to computer evaluation, but creates extreme complications for the opponent and creates practical chances for the player who played it, and thus is extremely hard to refute over the board. Tal moves almost always sacrifice material for some sort of positional advantage, opening up lines of attack, deflecting an important defender, interposing a piece to disconnect enemy pieces, or injecting poison into an otherwise stable position. Refuting a Tal move often requires violating cherished chess principles or finding an unusual only move.
The Tal move is, of course, named after legendary Latvian grandmaster and one-time world champion Mikhail Tal, aka the "Magician of Riga," who played many such moves in his long and storied career. As Tal himself said, "You must take your opponent into a deep dark forest where 2+2=5, and the path leading out is only wide enough for one." Similarly, Tal recognized that many of his bold sacrifices were actually quite dubious, stating that "There are two types of sacrifices in chess: sound ones, and mine."
Tal moves often look silly when plugged into a modern computer chess engine, because the computer can often instantly find a line that completely refutes the move and destroys the position of the player that played it. But that is precisely the beauty of playing a Tal move in a game between actual human beings. Everyone knows it is a terrible move right away, but nobody can figure out why or how to defeat it, until they go check with the computers after the game is over.