In a manner that is unhelpful, harmful, or not serving a useful purpose.
Adverbial form created by adding -ly to disserviceable. The -ly suffix converts adjectives to adverbs, a pattern originating in Old English -lice. This regular word formation process has been productive in English for over a thousand years.
The -ly adverb suffix is so powerful that we can turn almost any adjective into an adverb describing how something happens. It's one of the most reliable word-building tools in English, used thousands of times per day.
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