https://en.wikipedia.org/wiki/Chub_%28gay_slang%29
These definitions are general in nature; specific definitions may vary depending on the perspective of the individual.

Chubby or chub – a large, overweight, or obese man
Superchub – a chub who is extremely large
Bear – a man with a stocky or heavyset build; typically hairy body and facial hair; sometimes older (or older looking) and displaying a masculine appearance and mannerisms
Chubby bear – a bear who is particularly large; this term has risen in use as the term "bear" has become more mainstream and broadened to include smaller men
Chaser – a man who is of smaller body size and/or stature who is sexually or romantically attracted to chubs or bears. The term chaser is sometimes used in various communities to describe an outsider who is sexually attracted to people within the community
Chub for chub (also referenced as chub4chub, internet shorthand) – a chub who is sexually or emotionally attracted to other chubby men
Girth & Mirth – a formerly widespread name for clubs of big men and their admirers
Big Men's Club – another term used to define clubs and organizations for gay and bisexual men and their male admirers