IPA: /ˈtrʌbəlˌsʌm/
KK: /ˈtrʌbəlˌsʌm/
Causing problems or worry; something that is difficult to deal with.
The troublesome child kept interrupting the class.
Comparative: more troublesome
Superlative: most troublesome
Troublesome → It is formed from "trouble" (from Old French *trouble*, meaning disturbance or confusion) and "-some" (meaning characterized by). The word "troublesome" means characterized by causing trouble or disturbance.
Think of something that is 'characterized by' ('-some') causing 'disturbance' ('trouble') — that's why troublesome means it causes trouble.