This data set gathered from appendix A includes 182 English words. Source words are either ambiguous or unambiguous.
rgm2002a
A data.frame with 182 rows and 2 variables:
Orthographic representation.
Whether or not the word has more than one meaning: Y (yes) or N (no)
Rodd, J., Gaskell, G., & Marslen-Wilson, W. (2002). Making Sense of Semantic Ambiguity: Semantic Competition in Lexical Access. Journal of Memory and Language, 46(2), 245-266. doi:10.1006/jmla.2001.2810
See source paper for details.