"barricade defense made of felled trees with the branches angled outward," 1766, from French abatis, literally "things thrown down," from Old French abateiz "a casting down; slaughter, carnage" (12c.), from abatre "to beat down, throw down" (see abate).

"destitute of color; transmitting light without decomposing it into constituent colors," 1766, from a- (3) "not, without" + chromatic. Related: Achromatically.

"sub-acidic, slightly sour" (of cream of tartar, oranges, etc.), 1766, also used figuratively for "sour-tempered;" from Latin acidulus "slightly sour," a diminutive of acidus (see acid (adj.)).

"of or pertaining to or engaged in agriculture," 1766, from agriculture + -al (1). Related: Agriculturally; agriculturalist.

"an opening to admit or discharge air," 1766, from air (n.1) + hole (n.).

1766, "pretentiously jaunty," from airy "with ostentatious air" + -ly (2).

"pertaining to archaeology," 1766, in the antiquarian sense, from archaeology + -ical. Earlier was archaeologic (1731). Related: Archaeologically.

1766, a misapplication to the European bison (Bos bison) of a word that actually refers to a species of wild cattle (Bos ursus) that went extinct early 17c.; from German Aurochs, from Old High German urohso, from uro "aurochs" (cognate with Old English ur, Old Norse ürr), which is of unknown origin, + ohso "ox" (see ox). Latin urus and Greek ouros are Germanic loan-words.

1766 in geography, from French Australasie (De Brosses, 1756), "Australia and neighboring islands," also used later in zoology in a somewhat different sense (with reference to Wallace's line); see Australia + Asia. Related: Australasian.

"sluggish watercourse, outlet of a lake or river," 1766, American English, via Louisiana French, from Choctaw (Muskogean) bayuk "small stream."