They define the feature recall of w with respect to v as the weighted proportion of features of v that also appear in the vector of w. Then, they suggest that a hypernym would have a higher feature recall for its hyponyms (specifications), than vice versa.
their results in predicting the hyponymy-hyperonymy direction (71% precision) are comparable to the naïve baseline (70% precision) that simply assumes that general words are more frequent than specific ones.