The noun plenitude means the state of being full or complete; also, an abundance. After the thirty inches of snow your town got over the weekend, you may joke that you have a plenitude of snow.
You can remember the meaning of plenitude if you remember that both plenitude and the word plenty come from the same Latin word plenus, meaning full or complete. Note that the spelling of plenitude has only one "t," although people misspell the word as plentitude because they closely relate plenitude and plenty. You can even find the variant spelling in some dictionaries.