adverb taking the 'to' particle
Mimetic adverb describing a continuous hissing or swishing sound, such as steam escaping, frying, or something moving quickly through the air. Often used with と.
やかんがシューシューと湯気を立てている。
The kettle is hissing with steam.
フライパンで肉がシューシュー音を立てて焼けている。
The meat is sizzling in the frying pan.