noun. ['ˈjuːnəsən, ˈjuːnɪsən'] occurring together or simultaneously.
noun. ['ˈjuːnəsən, ˈjuːnɪsən'] (music) two or more sounds or tones at the same pitch or in octaves.
noun. ['ˈjuːnəsən, ˈjuːnɪsən'] corresponding exactly.