The degree to which meanings are related in memory affects ambiguous word processing. We examined irregular polysemes, which have related senses based on similar or shared features rather than a relational rule, like regular polysemy. We tested to what degree the related meanings of irregular polysemes (wire) are represented with shared semantic information versus unshared information represented separately, like homonyms (bank). Monitoring eye fixations, we found that later context supporting the less frequent meaning of an irregular polyseme did not slow down reading compared with control conditions, whereas for homonyms it did. This indicates that in the absence of preceding biasing context, readers access a shared component of an irregular polyseme’s representation. Additionally, when the same context words preceded the ambiguous word, both irregular polysemes and homonyms initially elicited longer reading times, but the observed reading slow-down was weaker and less persistent for irregular polysemes than homonyms, indicating less competition between meaning components. We interpret these results as evidence of a shared features representation for irregular polysemes, which additionally incorporates unshared portions of meaning that can compete. When preceding, biasing context is available, readers activate shared and unshared components of the senses, producing a more fully instantiated meaning.