thagomizer
An arrangement of spikes found on the tails of various stegosaurs.
Like the thagomizer of the stegosaur, the ankylosaurid tail club was probably used to smash into attackers.
Where it comes from
Coined by cartoonist Gary Larson in 1982. His comic strip (image on the right) shows a caveman giving a lecture illustrating this part of a dinosaur, with the caption "Now this end is called the thagomizer... after the late Thag Simmons". See -ize, -er.
Adapted from the Wiktionary entry thagomizer (CC BY-SA 4.0).