The phrase "to undergo an operation" means to have a medical procedure or surgery performed on one's body to treat a health condition or problem. Full definition
He quickly had to undergo an operation on his knee to have a torn cartilage removed and a loose ligament tied. (si.com)
After undergoing the operation, you will start to rapidly lose weight. (blog.nkdnutrition.com)
Some of the patients originally assigned to the «no surgery» group did undergo the operation during the study, the researchers noted. (criticalillnessinsuranceinfo.org)