In this review article, we discuss the construct of second language (L2) comprehensibility, which refers to listeners' judgments of ease or difficulty in understanding L2 speech. We first briefly describe intelligibility and comprehensibility, two measures that capture listener understanding of L2 speech. We then present evidence that supports the value of comprehensibility as a measure of understanding. We outline findings showing that L2 comprehensibility can be socially influenced, dynamic, and linked to multiple elements, both language-related and other. Finally, we discuss how researchers, teachers, as well as speakers and listeners can approach L2 comprehensibility in ways that account for its nuanced and complex nature.