What is it? What does it mean?

The Bucket List (Wikipedia article) is a 2007 movie about two men (Morgan Freeman and Jack Nicholson) with terminal cancer. One (Morgan Freeman) makes a "bucket list" of things he wants to do before he kicks the bucket.

Urban Dictionary has a different, more sickening, definition of the phrase.

Actually it's French, thus "bouquet" list of possible floral arrangements a bride can carry.

I guess you've not seen the Britcom, "Keeping Up Appearances," Proof. There's a Mrs. Bucket who pronounces it "Bouquet."
http://en.wikipedia.org/wiki/Keeping_Up_Appearances