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drop-off
drop-off n. 
/ˈdrɑpˌɑf/ an act of dropping off (see to drop off at drop v. Phrasal verbs); spec. a diminution; also attributive.
Brit. /ˈdrɒpɒf/
, /ˈdrɒpɒf/U.S. /ˈdrɑpˌɔf/
, /ˈdrɑpˌɔf//ˈdrɑpˌɑf/ΚΠ
1925 Duo-Art Reproducing Piano: Service Man. (Aeolian Co.) 14 Drop-off screw.
1952 Time 21 Apr. Drop-off point, place where copies of Time come off a plane, train or truck.
1958 College Eng. 20 16/2 There is no drop-off in volume.
1959 Times 31 Jan. 6/1 The rocket engines are fuelled by a mixture of liquid oxygen and ammonia representing about half the drop-off weight of 31,275 lb.
drop-off
drop-off n. /ˈdrɑpˌɑf/ Originally and chiefly U.S. a steep descent or dropping away of the ground, on land or underwater; a declivity; also, the brink above this.
Brit. /ˈdrɒpɒf/
, /ˈdrɒpɒf/U.S. /ˈdrɑpˌɔf/
, /ˈdrɑpˌɔf//ˈdrɑpˌɑf/ΚΠ
1923 C. F. Saunders Southern Sierras Calif. 204 It was a climb of many short turns and dizzy drop-offs.
1955 National Geographic Mag. July 85/1 A dizzying 13-mile drive up the mountainside, around hairpin curves, along harrowing dropoffs, had brought us from a valley floor elevation..to our present altitude.
1969 Guardian 8 Mar. 7/5 Beyond the dropoff of the continental shelf, the waters of the Indian Ocean are clear and dark blue.
1985 T. O'Brien Nucl. Age v. 86 There was the strange, somewhat dizzy sensation of moving blindfolded toward a steep drop-off.
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as lemmas