What does "ads" mean?

Brad tends to say "ads" a lot, especially during Destiny quick looks. What does it mean? I can't find a definition of it anywhere.

I know in some circles it means Aim Down Sights, but then what does Brad mean when he says "we gotta clear out these ads"?

thanks in advance

Additional enemies, who appears when a trigger activates.

Additional badguys that come into a fight after it's started. MMO term.

cool thanks