phrasal
1.
a. : to turn loose or free from restraint : let go : liberate
floating mines, evidently let loose by French patrols — P.W.Thompson
an entomologist who was let loose on the same small area — C.W.M.Swithinbank
the rancors let loose by war — J.D.Hicks
b. : to give rise to : set off
the great success of the pioneer lines let loose a torrent of speculative buying — O.S.Nock
2. : to let fly
I do now let loose my opinion — Shakespeare
let loose a torrent of invective — Albert Dasnoy
let loose a tremendous outburst of laughter — Walter O'Meara
a machine gun let loose on me — Mack Morriss
specifically : to pour down rain
get the shocks into the stack before the skies let loose — Irving Dilliard
3. : to throw off restraint : let go : give way
the friction clutch would let loose at its appointed tension — F.J.Haskin