Definition of counter- in US English:

counter-

prefix

  • 1Denoting opposition, retaliation, or rivalry.

    ‘counterattack’
    ‘counterespionage’
    1. 1.1 Denoting movement or effect in the opposite direction.
      ‘counterpoise’
      ‘counterbalance’
    2. 1.2 Denoting correspondence, duplication, or substitution.
      ‘counterpart’
      ‘counterpoint’

Origin

From Anglo-Norman French countre-, Old French contre, from Latin contra ‘against’.

Pronunciation

counter-

/ˈkaʊn(t)ər//ˈkoun(t)ər/