Peak inverse voltage (PIV)
also known as: Reverse voltage rating · V_RRM
The maximum reverse voltage a diode can block before it avalanches and conducts backwards — usually destructively for parts not designed to do so. Every blocking diode in a design has a worst-case reverse voltage; PIV must comfortably exceed it.
In practice
Rectifiers see roughly twice the peak AC voltage in reverse; a 'blocking' diode on a battery sees the full charger voltage. PIV is cheap — the 1000 V 1N4007 costs the same as the 50 V 1N4001 — so the only failure here is not checking.