1A theoretical or conceptual model which deals primarily with the behaviour of a system as a whole, rather than that of its constituent elements; a model that takes into account large-scale, global, or systemic factors; (Economics) a macroeconomic model.

2Electronics. In the computer simulation of electronic circuits: a model which represents a complex device or network as a circuit composed of elementary components, whose overall behaviour approximates that of the modelled device, while differing from the latter in configuration.

3Chiefly Biology and Chemistry. A physical model of a small-scale (especially microscopic) structure at a larger scale than the original, designed to simulate physical characteristics or behaviour which might be difficult to observe directly in the structure itself.