1. being well versed (in), being well acquainted (with), being familiar (with), having a thorough knowledge (of), being an authority (on)

noun or participle which takes the aux. verb suru intransitive verb noun (common) (futsuumeishi)

2. (a boy's) first ejaculation, spermarche, semenarche

intransitive verb noun or participle which takes the aux. verb suru noun (common) (futsuumeishi)