1: the process of growth or enlargement by a gradual buildup: as
a : increase by external addition or accumulation (as by adhesion of external parts or particles)
b : the increase of land by the action of natural forces
2: a product of accretion; especially : an extraneous addition <accretions of grime>
I love the word because it describes life so well. Life is a process of buildup and accumulation, both intentional and unintentional. I don't mean accumulation in a material sense as in possessions or wealth but rather in the sense that our lives are a buildup of experiences, ideas, interactions with people, etc. The things that we 'accrete' make us who we are.
As we grow older and wiser we (hopefully) recognize the things that have shaped us - some beneficial, some not. Some accretions need to be scraped off and shaken off; some accretions need to be protected and nurtured.
Accretion - a great word.