adverb / ~と adverb:

• fiercely (e.g. of a fire burning) - onomatopoeia
• bong-bong (of clock ringing) - onomatopoeia
• with repeated bangs (e.g. of fire cracker) - onomatopoeia

noun:

• striking clock - abbreviation - onomatopoeia ➜ ぼんぼん時計
• green young man from a well-to-do family - Kansai dialect