A cylindrical container filled with some type of predominantly lipid substance. A can of grease could be used for cooking, or it could be used for hair styling. Depends on the grease.

In NetHack, a can of grease is a charged item that allows you to fix those pesky squeaky boards. Oddly enough, you earn points at the end of the game for each board you grease up. A can of grease can also be used to rustproof weapons and armor. If you apply the grease to your outermost armor, grabbing attacks won't affect you. Note, however, that the grease has a 50% chance of wearing off after each attack it protects against. The can of grease can be recharged by the usual methods. It starts off with 1 to 25 charges.