A 5250 Psychiatric hold is a welfare and institutions code that allows allows a qualified officer or clinician to involuntarily confine a person deemed to have certain mental disorders for up to 14 days, following being involuntarily held for 72 hours.
So if you've been held for 72 hours involuntarily and the qualified clinician or officer deems it necessary to hold you longer than 72 hours then they can hold you for up to 14 days longer under the 5250 Psychiatric hold.