adverb, adverb taking the 'to' particle
gushing out; pouring out in large amounts
Mimetic word describing liquid or granular substances flowing out forcefully and in large quantities. Often used with と.
水道の蛇口をひねると、水がどばどばと出てきた。
When I turned on the faucet, water came gushing out.
袋が破れて、米がどばどばとこぼれた
The bag tore and rice poured out in a rush.
Onomatopoeic/mimetic word; the exact derivation is uncertain, but it phonetically suggests a heavy, gushing sound.