(pharmacology, of medicine and other treatments) Legal for sale or distribution without the requirement of a prescription.

(fencing) A parry that is done to defend against an opponent's parry and riposte.

(fencing) An attack that responds to the opponent's counter-attack.

Alternative form of countertenor

An attack made in response to an attack by the opponents

To attack in response to an attack by opponents.

(finance) Through direct trade; outside a standard stock exchange. / (pharmacy) Able to be obtained without a doctor's prescription. / (figuratively) Legitimately.

Alternative spelling of counterintelligence

(idiomatic) A person who has an obsession with the minutiae of their particular interest, especially in military and technology history. Anyone preoccupied with small distinguishing features between different items.

Measures intended to combat or reduce terrorist activities.