short version is that words mean many different things depending uponones own location, language.....

if you are here in New York (the one in the USA, as opposed to other locations dis association means to purposely not associate with something, purposely stop what you are doing...

Examples....

I disassociated myself from being a member of the soft ball team ....meaning I purposely quit the team

I disassocated myself from my job for two weeks....meaning I purposely stopped myself from working for two weeks.

I did not like the movie I was watching so I disassociated myself from it....meaning I purposely stood up and changed the channel rather than sitting there continuing to watch something I did not like.

if you mean what is dissociation which is different than disassociation here in NY.....

here in NY dissociation is a reaction to a trigger....feeling numb, spacey, foggy minded,

example

I saw someone that reminded me of my abuser. when that happened I felt numb, like I had no emotions.