i-adjective
grassy; weedy; overgrown with grass
Describes a place where grass or weeds grow thickly, often with a nuance of being wild or untended.
庭が草深くなってしまった。
The garden has become overgrown with grass.
草深い道を歩くのは大変だ。
Walking along a weedy path is tough.
草ぼうぼう is a more colloquial and emphatic expression for a place being extremely overgrown with grass or weeds, while 草深い is a standard adjective.
Compound of 草 (kusa, 'grass') + 深い (fukai, 'deep'). The reading ぶかい is a rendaku form of ふかい.