Double-dip recession
A double dip is two distinct recessions joined by a recovery too brief to restore the economy — a W-shaped path instead of a V. The textbook case is 1980 and 1981–82: a six-month contraction, twelve months of expansion, then a 16-month recession deeper than the first.
Why it happens
Double dips usually trace back to policy or unfinished shocks. In 1980–81, Volcker's Fed eased when inflation dipped, saw it rebound, and slammed rates back up — the second recession was the price of crushing inflation that the first recession failed to finish.
Why it matters for signals
Double dips confound signal interpretation: indicators can stay elevated through the 'recovery' or re-fire after briefly clearing. This site lists 1980 and 1981–82 as separate episodes — matching NBER's treatment — so the signal record shows both dips independently.