Noun
びーだま
ビーだま
ビー玉をつかってゲームをしましょう。
Let’s play a game that uses marbles.
アメリカではまいとし一月にビー玉をつかったゲームが上手なフランス人がつどうコンテストがあります。
In America, there is a contest every January where French people who are good at marbles gather.
かれは、けっこんのあかしに一つぶのビー玉をくれた。
He gave me a single marble as proof of our marriage.
Presumably this ビー is short for the word "bead." Beads used to be glass, which means that if you have a glass bead ball, you probably have yourself a marble.
If you know katakana as well as the reading that you learned when you learned the kanji 玉, you should be able to read this. Just watch out for the rendaku.