also: そこぶかい
i-adjective
very deep; profound
Describes something physically deep, such as a valley or forest, or metaphorically deep, like a thought or emotion. Often implies a sense of depth that is hard to measure or reach the bottom of.
底深い谷をのぞきこむと、足がすくんだ。
When I peered into the very deep valley, my legs froze.
彼の言葉には底深
A profound sadness could be felt in his words.