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3.
Adders: short for advantage. To take adders is to make sexual advances to someone who is in a state where they cannot give consent, being drunk or asleep are the most common two states for adders to take place.
Tim: Hey, look Hollie's passed out

Mike: I think you should take adders whilst you can

Tim: Yeah good idea, i'll be back in 2 minutes
by Dr Two Step August 10, 2010
 
1.
1. A snake

2. Someone that adds everyone they see on a social networking site for friends
That adder Bob, he added all my friends even though he doesn't know them!
by Toillek November 16, 2007
 
2.
a posonious snake
Steve Irwin almost got bit by an adder.
by Michael LaCombe April 21, 2003