flank
https://gyazo.com/80c0112484dde41da296818778fb74db
source: [ゆゆ式の日向縁が櫟井唯の脇腹を突くGIF画像｜無料GIF画像検索 GIFMAGAZINE 100623]
noun
1. the side of a person's or animal's body between the ribs and the hip:
(動物･人の)脇腹, 横腹〘ろっ骨と尻との間〙
e.g. leaning against his horse's flanks.
a cut of meat from the flank of an animal:
(牛などの)脇腹肉の切り身
e.g. a thick flank of beef on a spit
e.g. two pounds of flank.
the side of something large, such as a mountain, building, or ship:
｟かたく｠ (山･建物の)横側, 側面(side)
e.g. the northern flank of the volcano.
2. the right or left side of a body of people such as an army, a naval force, or a soccer team:
(戦場の部隊の)側面; (サッカーなどの)サイド(wing)
e.g. the left flank of the Russian Third Army.
the right or left side of a game board such as a chessboard.
(チェス盤などの左右の)側
verb with object
be situated on each side of or on one side of (someone or something):
〈人･物〉の(両)側に立つ, ある, 位置する (!しばしば受け身で)
e.g. the fireplace is flanked by built-in bookshelves.
(usually as adjective flanking) guard or strengthen (a military force or position) from the side:
〘軍〙 …を側面を守備する; …の側面を迂回（うかい）する
e.g. massive walls, defended by four flanking towers.
(usually as adjective flanking) attack down or from the sides, or rake with gunfire from the sides:
〘軍〙 …を側面攻撃する
e.g. a flanking attack from the northeast.
ORIGIN
late Old English, from Old French flanc, of Germanic origin.