Adjective used to decribe old people,a gross unidentified substance, anything broken, dirty, crumby, badly made/conceived, falling apart, stupid, wierd, gross, this word can be used very freely as it goes with anything that may have to do with the word crust but it never describes anything good.
1: that old man keeps staring at me
2: eww look how crusty he is
1: i just got this from the dollar store and the lid wont close on it
2: here let me try... damn its not working it sooo crusty
1:that whole dollar store is crusty
1:Mr Tawil thinks he can teach us history by giving us a whole bunch of crosswords, he is such a crust.
2:Yea, he smell like weed, cigarettes and bagels, he is such a crusty old man.
1:ew look at the crust under this desk
2: that's gum , you dumbass