It's the present participle of the verb "Reminisce", which is a synonym for the verb "Remember".
It is a very classy verb used by various poets and people of higher status.
It was also made famous by rapper Tupac Shakur's "Pour out a little liquor" song which made various Afro-American L.A. gangsters use it while smoking weed and drinking liquor with their bitches in the club.
Person 1 : Yo wazzup man! Watchu u doin here sHHmokin' that weed all alone?
One who masters in the art of reminiscing. A professional reminiscer who works to push the field of reminscing further by innovating new reminiscing techniques.
Dr. Van Nostrum works as a reminiscintologist, he helped me recall the events that took place on that one fatefull summer.