A dikaryon means
a cell with two haploid nuclei formed after plasmogamy
In some fungi, plasmogamy (the fusion of protoplasts between two haploid cells) immediately results in diploid cells (2n). However, in other fungi (ascomycetes and basidiomycetes), an intervening dikaryotic stage (n + n i.e., two nuclei per cell) occurs; such a condition is called a dikaryon and the phase is called dikaryophase of fungus. The parental nuclei then fuse and the cells become diploid. This is followed by meiosis.