This is when the objects are deformed or stick together. Momentum is still conserved in these situations, but this time the objects do not escape the collision unharmed. And unlike elastic collisions, inelastic collisions do give off quite a bit of heat when the two objects come together.
From Wikipedia: Curtana, also Cortana or Courtain, is a latinized form of the Anglo-French curtein, from Latin curtus, 'shortened', used for a ceremonial type of sword. [...] Curtana was also, according to legend, the sword of Ogier the Dane; it bore the inscription My name is Cortana, of the same steel and temper as Joyeuse and Durendal..
Cortana is a fictional artificial intelligence character in the Halo video game series. Voiced by Jen Taylor, she appears in Halo: Combat Evolved and its sequels, Halo 2, Halo 3, Halo 4 and Halo 5: Guardians. She also briefly appears in the prequel Halo: Reach, as well as in several of the franchise's novels and comics. During gameplay, Cortana provides backstory and tactical information to the player, who assumes the role of Master Chief Petty Officer John-117. In the story, she is instrumental