Learner's definition of MARBLE
1 [noncount] : a kind of stone that is often polished and used in buildings and statues — often used before another noun 2 a [count] : a little glass ball used in some children's games b marbles [noncount] : a children's game played with little glass balls
lose your marblesinformal + humorous
: to become insane
When he started ranting about how the government was out to get him, I thought he'd lost his marbles. [=gone crazy]
He hasn't completely lost his marbles yet.