coaction

1. An impelling or restraining force; a compulsion.
2. Joint action.
3. Ecology. Any of the reciprocal actions or effects, such as symbiosis, that can occur in a community.

[Middle English coaccioun, from Latin coāctiō, coāctiōn-, a collecting, from coāctus, past participle of cōgere, to collect, condense. See coagulum. Senses 2 and 3 : CO- + ACTION.]

noun

Joint work toward a common end: collaboration, cooperation, synergy, teamwork. See conflict/cooperation.

1. A situation in which two or more individuals are engaged in the same activity at the same time. The general affect of coaction is to raise arousal levels. Individuals who are optimally aroused for a sporting event may become overaroused when joined by other individuals. This may lead competitors to perform less well and spectators to become aggressive. The larger the number of people engaged in an activity and the closer their proximity to one another, the greater the coaction effects will be.

2. The interaction between two or more individuals, which produces a motivating effect on performance. Compare audience effect, social facilitation. See also dynamogeny, social interactive forces.

The noun has one meaning:

Meaning #1: act of working jointly
  Synonym: collaboration