back + -ward

source: [がっこうぐらし！の丈槍由紀が恐怖で後ずさるGIF画像｜無料GIF画像検索 GIFMAGAZINE 662730]

1. attributive directed behind or to the rear:

比較なし 〖通例名詞の前で〗後ろ(へ)の, 後ろ向きの〈動作･視線など〉(↔ forward)

e.g. she left the room without a backward glance

e.g. a gradual backward movement.

looking toward the past, rather than being progressive; retrograde:

悪化, 退化して

e.g. he said the decision was a backward step.

2. having made less than normal progress:

〈国･社会などが〉進歩, 発展の遅い(→ developing)

e.g. economically backward countries.

dated or offensive (of a person) having learning difficulties:

｟やや古･けなして｠ 〈子供などが〉物覚えの悪い, 知恵遅れの.

e.g. a lively child but a bit backward.

adverb (also backwards)

1. (of a movement) away from one's front; in the direction of one's back:

後ろへ, 後方へ(↔ forward)

e.g. he took a step backward

e.g. Harry suddenly fell backward into a somersault.

in reverse of the usual direction or order:

逆に, 逆さに; 後ろ前に

e.g. counting backward

e.g. baseball caps turned backward.

2. toward or into the past:

過去にさかのぼって.

e.g. a loving look backward at his early life.

toward or into a worse state:

悪化, 退化して

e.g. a giant step backward for child-centered education.

in both directions alternately; to and fro.

informal make every effort, especially to be fair or helpful: Jensen bent over backward to be fair.

be entirely familiar with something.

backwardly | ˈbakwərdlē | adverb

Middle English: from earlier abackward, from aback.

In US English, the adverb form is sometimes spelled backwards ( the ladder fell backwards), but the adjective is almost always backward ( a backward glance). Directional words using the suffix -ward tend to have no s ending in US English, although backwards is more common than afterwards, towards, or forwards. The s ending often (but not always) appears in the phrases backwards and forwards and bending over backwards. In British English, the spelling backwards is more common than backward.