This norming study examines the metaphoricity of 99 English crossmodal expressions called “synesthetic metaphors”, such as sweet voice and vivid memory. American English speakers rated how metaphorical each of the synesthetic metaphors is and how easily the synesthetic meaning of the adjective can be separated from its original meaning (adjective ambiguity). The results revealed four key findings. (1) Some synesthetic metaphors were rated more metaphoric than others, and their metaphoricity was positively correlated with their adjective ambiguity. (2) Synesthetic metaphors with sensory nouns were rated as metaphorical as those with non-sensory nouns that are assumedly more metaphorical. (3) Synesthetic metaphors that combine taste and smell words were rated low in metaphoricity. (4) The emotional valence of the adjectives did not influence the metaphoricity of synesthetic metaphors. These findings suggest that, contrary to some previous proposals, some synesthetic metaphors do involve metaphorical mappings and are more than mere evaluative expressions.