noun
Colloquial term for 'eyeball', equivalent to the more standard 目玉 (めだま). Often used in casual speech or with a slightly rough, emphatic tone.
See also: 目玉
目ん玉が飛び出るほど驚いた。
I was so surprised my eyeballs nearly popped out.
あいつ、目ん玉だけはでかいんだよな。
That guy's got huge eyeballs, you know.