To disillusion (someone) is to free or deprive (him or her) of an illusion. For example, someone who has always thought Batman to be real might be disillusioned upon learning he is a fictional character. Dissolution is a noun—its corresponding verb is dissolve—referring to (1) decomposition into fragments, (2) indulgence in sensual pleasures, (3) annulment of a formal legal bond or contract, (4) formal dismissal of an assembly, and (5) reduction to a liquid form.
Though disillusion is primarily a verb, it’s most commonly used in the participial adjective disillusioned, meaning deprived of illusion. Disillusion also works as a noun referring to (1) the act of disillusioning, and (2) the state of being disillusioned, but the word usually gives way to disillusionment for these senses.
Because they’re almost homophones, disillusion and dissolution are occasionally confused—for example:
As the successor, the city will oversee the disillusion of the agency. [Big Bear Grizzly]
During this time Alan never allowed the relentless attack to the scout property to dissolution him or smother his enthusiasm for Scouting. [quoted in Wear Valley Mercury]
These writers use the words well:
Because Obama needs to stir the passions and enthusiasms of a Democratic base that’s been disillusioned with his cave-ins to regressive Republicans. [Huffington Post]
The dissolution of the Soviet empire in Europe, and Havel’s ascent to the Czech presidency, was tidier than we had any right to expect. [Telegraph]
Manning, who was posted to Iraq in 2009 and grew increasingly disillusioned with the military and US foreign policy, apparently believed he was acting for a just cause. [Sydney Morning Herald]
The deal later led to the dissolution of a paper factory in Indiana. [Wall Street Journal]