A friend; a pal.
I ran into an old chum from school the other day.
A roommate, especially in a college or university.
To share rooms with someone; to live together.
To lodge (somebody) with another person or people.
To make friends; to socialize.
To accompany.
I'll chum you down to the shops.
To cast chum into the water to attract fish.
A coarse mould for holding the clay while being worked on a whirler, lathe or manually.