To perforate means to make a hole or series of holes through something. When you use a hole punch on paper, you perforate it. Postage stamps are perforated along their edges with tiny holes so you can tear them apart easily without scissors.

A perforated line is a row of small holes that makes something easy to tear, like the edge of a notebook page or a ticket stub. Doctors also use this word: a perforated eardrum has developed a hole in it, usually from infection or injury.

You might perforate aluminum foil with a fork to let steam escape when baking. Farmers perforate drainage pipes so water can seep through. The holes can be large or small, one or many, but they always go all the way through the material. If you only make a dent or dimple without breaking through to the other side, that isn't perforation.