The difference between Foul-smelling and Smelly

When used as adjectives, foul-smelling means having an unpleasant odor, whereas smelly means having a bad smell.

Smelly is also noun with the meaning: a short magazine lee enfield rifle or one of its derivatives.

check bellow for the other definitions of Foul-smelling and Smelly

Smelly as an adjective:

Having a bad smell.

Examples:

"She was hesitant to remove her shoes, as her socks were rather smelly."
Smelly as an adjective (figuratively):

Having a quality that arouses suspicion.

Examples:

"The detective read the documents and thought, "Something sure is smelly about this case."
Smelly as an adjective (figuratively, computing, slang, in [[extreme programming]]):

Having signs that suggest a design problem; having a code smell.

Examples:

"That smelly code needs to be refactored."

Smelly as a noun (firearms, informal):

a Short Magazine Lee Enfield rifle or one of its derivatives.