Definition of "thopter"

Another ’thopter glided in over the cliff wall above Hawat. He drew in a sharp breath as he saw it—a big troop-carrier. It flew with the slow, spread-wing heaviness of a full load like a giant bird coming to its nest.

1965, Frank Herbert, Dune, New York: Ace Books, page 225

I'm sending down five more dropships, combat EMVs, and a thopter gunship.

1997 September, Dan Simmons, The Rise of Endymion, New York: Bantam, page 363

Flowstone Thopter gets +1/-1 and gains flying until end of turn.

2000 February 14, “Flowstone Thopter”, in Magic: The Gathering, Nemesis, Wizards of the Coast