a. Law Existing or entered into by mutual consent without formalization by document or ceremony: a consensual marriage; a consensual contract.

b. Involving the willing participation of both or all parties, especially in an illegal transaction or practice: the consensual crimes of prostitution, drug abuse, and illegal gambling.

a. Of or relating to a reflexive response of one body structure following stimulation of another, such as the concurrent constriction of one pupil in response to light shined in the other.

b. Of or relating to involuntary movement of a body part accompanying voluntary movement of another.