Survey respondents misunderstand questions often enough to compromise the quality of their answers. Web surveys promise to improve understanding by making definitions available to respondents when they need clarification. We explore web survey respondents’ use of clarification features in two experiments. The first experiment demonstrates that respondents rarely request definitions but are more likely to do so when they realize definitions could be helpful (i.e., definitions are available for technical terms) and when requests involve relatively little effort (i.e., just one click); respondents who obtained a definition requested more subsequent definitions when the initial one proved useful (i.e., included counter-intuitive of surprising information). In the second experiment, definitions available via mouse roll-over were requested substantially more often than when available via clicking, suggesting that some respondents find even a click more effort than they are willing to expend. We conclude with a discussion of interactive features in web surveys in general, when they are likely to be used and when they are likely to be useful.