The phrase Small Boys is used to describe the lowest form of what you could be doing at the time, for example, if you were to be on a poker table, a £100 table would be for the "Small Boys" whilst a £1,000,000 table would be for the big boys
"Oi Tom, You know if George got a 5 piece Chicken Meal for lunch like he said?"
"Nah mate, knowing him he went for a 1 piece kids meal, Small Boys he is"
In reference to someone (usually but not limited to male) begins displaying behavior that they'rejealous, have low self-esteem, and/or passive-aggressive especially towards their partner.
Guy: How many dudes have you slept with? Did you enjoy it? Were they better than me?
His gf: Why does it matter if you haven't noticed anything weird?
Guy: I just want to know.. because I'm curious.
His gf: Geez, what do you have, SDS (Small Dick Syndrome)?