Numerous definitions of teams exist in the research literature. One of my favorites comes from Kozlowski and Bell (2003). They state that teams:
“…are composed of two or more individuals who (a) exist to perform organizationally relevant tasks, (b) share one or more common goals, (c) interact socially, (d) exhibit task interdependencies (i.e., work flow, goals, outcomes), (e) maintain and manage boundaries, and (f ) are embedded in an organizational context that sets boundaries, constrains the team, and influences exchanges with other units in the broader entity.” (p. 334).
Kozlowski, S. W. J., & Bell, B. S. (2003). Work groups and teams in organizations. In W. C. Borman, D. R. Ilgen, & R. Klimoski (Eds.), Handbook of psychology: Industrial and organizational psychology: Vol. 12 (pp. 333-375). London: Wiley.