dummy bomb; fake bomb
Refers to a non-functional bomb used for training, display, or deception. Not a common everyday word, but straightforward in meaning.
訓練では擬爆弾を使って爆発物処理の手順を練習した。
In the training, we practiced bomb disposal procedures using a dummy bomb.
Compound of 擬 (gi, 'pseudo-') and 爆弾 (bakudan, 'bomb').