IPA: /ˈɡraʊliər/
KK: /ˈɡraʊlɪər/
More growly than something else; having a deeper or more pronounced growl.
The growlier dog barked louder than the others.
Comparative: growlier
Superlative: growliest
The word 'growlier' is derived from 'growl' (from Middle English 'growlen', meaning to make a low, guttural sound) and the suffix '-ier' (meaning one who or that which). Thus, 'growlier' refers to one who growls or is more inclined to growl.
Think of someone who is more likely to make a low, guttural sound ('growl') — the '-ier' indicates that this person is more of that quality.