tuff 1
/tuf/ , adj. Slang.
tough (def. 13).
tuff 2
— tuffaceous /tu fay"sheuhs/ , adj.
/tuf/ , n. Geol.
a fragmental rock consisting of the smaller kinds of volcanic detritus, as ash or cinder, usually more or less stratified. Also called volcanic tuff .
[ 1560-70; tuf tufo. See TUFA ]