-noun1. an act or instance of dissociating
2. the state of being dissociated; disjunction; separation
3. ( psychiatry ) the splitting off of a group of mental processes from the main body of consciousness, as in amnesia or certain forms of hysteria.
4. ( physical chemistry ) A. the reversible resolution or decomposition of a complex substance into simpler constituents caused by variation in physical conditions, as when water gradually decomposes into hydrogen and oxygen under great heat in such a way that when the temperature is lowered the liberated elements recombine.
B. electrolytic dissociation.