Both classic thought experiments and recent empirical evidence suggest that children frequently encounter new words whose meanings are underdetermined by the extralinguistic contexts in which they occur. The role that these referentially ambiguous events play in children's word learning is central to ongoing debates in the field. Do children learn words from referentially ambiguous events via an incremental learning process? Or, do children learn words primarily from the rare referentially transparent events they experience? Across two experiments with adults as model word learners, the current work asks whether the answer to these questions depends in part on how word learning is assessed. Participants were asked to learn the meanings of novel words solely from their referentially ambiguous contexts. When learning was assessed by asking participants to identify the exact meanings of those novel words, participants struggled mightily. However, when learning was assessed by asking the same participants to identify which of two new contexts the novel word most likely occurred in, even those who failed the exact meaning assessment succeeded. These data suggest that although referentially ambiguous events may fall short in allowing learners to identify a word's exact meaning, they nevertheless lead learners into the right regions of semantic space. These findings are a reminder of the pervasiveness of partial word learning effects in vocabulary acquisition and highlight that the resolution to the debate over the role of referentially ambiguous events in learning may depend on how learning is defined.