Adverb
Verb (する)
Onomatopoeic
1. slowly (but steadily); gradually; bit-by-bit
2. irritatedly; impatiently
3. scorchingly (of the sun)
4. sizzling (i.e. sound of frying in oil)
5. sound of a warning bell, alarm clock, etc.
6. oozing out (oil, sweat, etc.); seeping out