transitive verb
1.
a. : to touch off : ignite , explode
felt like a boy who wanted to let off crackers — I.L.Idriess
explosions produced by letting off small charges of dynamite backstage — W.L.Gresham
specifically : fire
let off their guns at British ships — G.F.Hudson
b. : to give vent to : get off
before I left I let off a dissent — O.W.Holmes †1935
2.
a. : to release from something, especially a penalty : pardon , excuse
the offender was let off with a severe reprimand — Harvey Graham
you have promised to sing one song … and I cannot let you off — W.H.Hudson †1922
b. : to release from duty
had let the men off for the last quarter of the day — Mary Austin
3. : to neglect an opportunity to dismiss or score against (an opponent)