In ancient times, fine undyed white silk was called 'gao'.
Tips
history
缟 is not used independently in modern Chinese. It survives only in classical texts and the four-character idiom 缟素 ('plain white mourning clothes'). The silk radical 纟 marks it as a fabric word; 高 supplies the sound with a tone change.
register
Literary and archaic only. You meet 缟 in old texts, poetry and etymology notes, never in everyday speech.