Verb hang back has 1 sense
  1. drag, trail, get behind, hang back, drop behind - to lag or linger behind; "But in so many other areas we still are dragging"
    --1 is one way to lag, dawdle, fall back, fall behind
    Sample sentences:
    Something ----s
    Somebody ----s
    Something is ----ing PP
    Somebody ----s PP
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