Interaction is an essential ingredient in any learning process. However, every interaction does not lead to increased learning. When interaction has a direct influence on learners' intellectual growth, we can say the interaction is meaningful. The precise meaning of meaningful interaction is strongly related to the learning theories underlying the development of particular learning environments. The primary goal of this paper is to re-conceptualize online interaction in terms of meaningful learning based on the learning theory known as social constructivism. Analyzing interaction through this theoretical framework may yield design principles needed to improve the quality of Web-based learning environments. A secondary goal of this paper is to present the implications of meaningful online interaction for researchers and developers.