This paper investigates learners' perceptions and interpretations of definitions from the 1995 editions of four major learners' dictionaries (OALD-5, LDOCE-3, COBUILD-2 and CIDE-1), and the Concise Oxford Dictionary 1990 (COD-8). 158 non-native speaker subjects were required not only to rate definitions in terms of their perceived helpfulness, but also to identify visual representations of them in a multiple choice format. Subjects were found to judge the definitions from LDOCE-3 and CIDE-1 as most helpful, and to interpret CIDE-I entries more successfully than the entries from OALD-5, LDOCE-3, COBUILD-2 and COD-8. The results help to distinguish those defining features which aid receptive and productive performance, while also identifying features open to misinterpretation. The number of subjects who were able to progress from incorrect production to correct identification also seems to indicate the value of including illustrations in dictionary entries for concrete nouns.