Rouse and Morris (1986):

A mental model is a mechanism whereby humans generate descriptions of system purpose and form, explanations of system functioning and observed system states and predictions of future system states

Others emphasized the notion of "shared" or "team" mental model, which is the development a common representation of the team's situation, that lead mutual expectation, and thus improved coordindation among team members (Cannon-Bowers and Salas, 1990). They proposed that team members form mental models of the external environment, the team environment, teammates, and the task, and that these are organised in a hierarchical manner. Those authors studies navy tactical decision making teams.