1.Fig. drinking liquor after a period of abstinence. (*Typically: be ~; fall ~; get ~.) Poor John fell off the wagon again. Drunk as a skunk.He was off the wagon for a year the last time before he sobered up.
2.Fig. back on drugs after a period of abstinence. (*Typically: be ~; fall ~; get ~.) Wilbur is off the wagon and shooting up again.He can't be off the wagon, because he has never stopped using, even for a day.