The Minotaur was a mythological half bull, half human creature. It lived in a Labyrinth on the island of Crete. It battled and was subsequently slain by Theseus.
The Lightning Thief
Percy Jackson flees from the Minotaur toward Camp Halfblood. It is described as being naked except for a pair of fruit of looms underwear.
After his morther Sally is thought to be killed by the Minotaur Percy jumps on the Minotaur's back pulls off its horn and stabs it in its side killing it.
By this time the Minotaur has reformed and is now general of Kronos' titan army. Percy defeated him once again this time at the Williamsburg Bridge.
In Last Olympian the Minotaur now had a weapon with him a giant axe with blades shaped like the letter Omega.