adverb taking the 'to' particle, taru-adjective
with a clang; clangingly
Describes a sharp, resonant metallic sound, often used in literary or descriptive prose. Functions as an adverb taking と or as a たる adjective.
鐘が戛然と鳴り響いた。
The bell rang out with a clang.
刀と刀がぶつかり、戛然たる音を立てた。
The swords clashed, producing a sharp clanging sound.
がちゃん is a more common onomatopoeia for a clang or crash, used in everyday speech, while 戛然 is literary and formal.
The kanji 戛 is rare and means 'halberd' or 'strike', combined with 然 (state). The exact derivation is uncertain; the word is a literary Sino-Japanese compound used to describe a metallic clang.