What is the definition or description of: chalazion?

A stye: A chalazion is a blocked oil gland in the eyelid that results in an area of lid swelling. A chalazion can feel like a pea on palpation of the eyelid. A doctor experienced at evaluating eyelids should make the diagnosis, because cancer can look similar to a chalazion (thankfully - these cases are rare). Treatment consists of hot compresses and steroids/antibioitcs. Surgery may be required.

Blocked oil gland: A blocked oil gland where the lashes meet the skin. The oil gets made but cannot get out, so it becomes trapped and stagnant and can get infected. Use warm compresses and see eye doctor as may need medicine and drainage.