Siddham script; Sanskrit script
Refers specifically to the Siddham script used in Japanese Buddhism to write Sanskrit mantras and seed syllables. Not a general term for any Sanskrit writing system.
I saw a stone monument carved with Siddham characters at the temple.
梵字は主に密教で用いられる。
Siddham script is mainly used in esoteric Buddhism.
Standard kanji spelling for the Siddham script used in Japanese Buddhism.
From 梵 (bon, 'Brahman; Sanskrit') + 字 (ji, 'character'). The term originally referred to any Indian script but became strongly associated with the Siddham script in Japanese Buddhism.