As a noun, the list of weblogs (blogs) on your blog that you like, or otherwise want to commend.
As a verb, the tactic of listing another's weblog in the hope that this will induce them to link to yours. Cf. if you don't go to other people's funerals, they won't come to yours.
You want links? Blogroll me!
A list of blogs that if, printed out, would supply you with enough loo paper for the next 10 years. Blogroll, due to it's shitty nature, makes excellent loo paper due to the universal law of attraction of similar particles.
Notice how the bullshit on the Blogroll absorbs mine so quickly.