monkeywrench

/M AH1 NG K IH0 R EH1 N CH/
noun
  1. 1

    A wrench (spanner) with an adjustable jaw.

  2. 2

    An unexpected or troublesome problem, obstacle or dilemma.

Source: https://en.wiktionary.org/wiki/monkey%20wrench, https://en.wiktionary.org/wiki/monkeywrench