Underwent is the past tense of the verb undergo, which means to experience something, especially something difficult, important, or transformative. When you say someone underwent surgery, they had an operation. When a caterpillar undergoes metamorphosis, it transforms into a butterfly.

The word carries a sense of going through something significant that happens to you rather than something you simply do. You wouldn't say you underwent breakfast, but you might say a building underwent major renovations, or that your town underwent changes after a new highway was built.

Undergo often describes challenging experiences: a patient undergoes treatment, an athlete undergoes intense training, or a scientist's theory undergoes rigorous testing. But it can describe any substantial process or experience, like when immigrants undergo the naturalization process to become citizens, or when a rough gemstone undergoes cutting and polishing to become a jewel.

The word suggests you're the subject of the experience rather than its active creator. You endure it, experience it, or pass through it. When your parents say you've undergone a growth spurt, they mean you've experienced a dramatic change, even though you didn't consciously make it happen.