Noisome means very bad-smelling or very unpleasant.
Noisome things are usually thought of as gross, disgusting, or very unpleasant.
Examples:
The noisome smell made me feel sick.
The garbage had a noisome odor.
Noisome things can make people feel very sick.
The noisome stench filled the room.
The noisome stink was so bad, it made people run away.
The noisome smell was the worst thing I ever smelled.