The non-embodied approach to teaching machines language is to train them on large text corpora. However, this approach has yielded limited results. The embodied approach, in contrast, involves teaching machines to ground abstract symbols in their sensory-motor experiences, but howor whether humans achieve this remains largely unknown. We posit that one avenue for achieving this is to view language acquisition as a three-way interaction between linguistic, sensorimotor, and social dynamics: when an agent acts in response to a heard word, it is considered to have successfully grounded that symbol if it can predict how observers who understand that word will respond to the action. Here we introduce a methodology for testing this hypothesis: human observers issue arbitrary commands to simulated robots via the web, and provide positive or negative reinforcement in response to the robots resulting action. Then, the robots are trained to predict crowd response to these action-word pairs. We show that robots do learn to ground at least one of these crowd-issued commands: an association between jump, minimization of tactile sensation, and positive crowd response was learned. The automated, open-ended, and crowd-based aspects of this approach suggest it can be scaled up in future to increasingly capable robots and more abstract language.