Slather (verb)

1. To spread a thick layer of something over a surface.
2. To apply (a substance) liberally or excessively.

Origin:

Early 19th century: of unknown origin.

Examples:

1. She slathered butter on her toast.
2. He slathered sunscreen on his arms and face.
3. The sandwich was slathered with mayonnaise.
4. The chef slathered the steak with sauce before grilling it.
5. He slathered on too much cologne and the smell was overwhelming.