noun
5 yen coin
Refers specifically to the Japanese 5-yen coin, a brass coin with a hole in the center. Often considered lucky because its pronunciation ごえん is homophonous with ご縁 (good connection/fate).
お賽銭に五円玉を入れた。
I put a 5-yen coin in the offering box.
五円玉は穴が開いている。
The 5-yen coin has a hole in it.
Compound of 五 (go, 'five'), 円 (en, 'yen'), and 玉 (dama, 'coin' or 'ball'). The reading ごえん is standard for 五円, and だま is a rendaku form of たま.