The Requirements elicitation involves knowledge intensive and collaborative activities. Requirements engineering research has proposed a range of knowledge elicitation and requirements gathering techniques, few of which apply specific strategies for eliciting tacit knowledge from stakeholders. The difficulty of taking the deliberate advantage of important tacit knowledge of stakeholders is one of the eminent problems in requirements elicitation. This paper proposes a model to define and elicit the tacit knowledge that has been generated during the requirements elicitation process. The model is based on adopting and extending the rationale model for requirements rationale knowledge elicitation in the requirements elicitation process context. Moreover, this paper presents a representation code to express the tacit knowledge in this context. Finally, to evaluate the feasibility of the model, a survey instrument was applied on domain experts to gather their opinion regarding the ability of the proposed model in facilitating tacit knowledge elicitation. In addition, controlled experiment used to evaluate the proposed model. To explore the model, a post-questionnaire was used to identify participants' feedback. The findings of the evaluation methodologies that were used showed that the proposed model can facilitate tacit knowledge elicitation in the requirements elicitation context. Also, the proposed model has a significant effect on improving the requirements elicitation. INDEX TERMS Requirements engineering, requirements elicitation process, rationale-based model, tacit knowledge.