Definitions

1. adjective

relating to or continuing from time immemorial, or from a time beyond memory

“The company has been trading immemorially in the same location.”

2. noun

a period of time from time immemorial

“The immemorial past has been shrouded in mystery.”

3. adverb

from time immemorial or since ancient times

“The village has been famous immemorially for its traditional festivals.”