source: [みおの顔が空洞になるGIF画像｜無料GIF画像検索 GIFMAGAZINE 356941]

1. having a hole or empty space inside:

〈物などが〉空洞の, からっぽの(↔ solid)

e.g. each fiber has a hollow core.

(of a thing) having a depression in its surface; concave:

〈(物の)表面が〉くぼんだ, へこんだ

e.g. hollow cheeks.

(of a sound) echoing, as though made in or on an empty container:

〖名詞の前で〗低く鈍い音で反響する; うつろな, 力のない〈音･声･笑いなど〉

e.g. a hollow cough.

2. without significance:

〖通例名詞の前で〗価値のない, 中身のない〈勝利など〉

e.g. the result was a hollow victory.

insincere:

〖通例名詞の前で〗うわべだけの, 本心からとは思えない, 感情がこもらない〈言葉など〉

e.g. a hollow promise.

a hole or depression in something:

穴, 空洞, 中空; くぼみ, へこみ

e.g. a hollow at the base of a large tree.

a small valley:

盆地, 谷間

e.g. the house fell behind as they climbed out of the hollow.

verb with object

form by making a hole:

…をくり抜く(out); «…を» くり抜いて…を作る(out) «of»

e.g. a tunnel was hollowed out in a mountain range.

make a depression in.

〈表面〉にへこみを作る, くぼみを付ける

defeat or surpass someone completely or thoroughly.

entirely in one's power:

e.g. great events lay in the hollow of his hand.

hollowly |ˈhälōlē| adverb

hollowness |ˈhälōnəs| noun

Old English holh‘cave’; obscurely related to hole.