* Part of a longer word: Most often, く is a component of a larger word, functioning as a syllable. For example, it's part of words like 書く (kaku - to write), 空く (aku - to become empty), 臭い (kusai - smelly), 苦い (nigai - bitter), etc.
* An abbreviation or informal shortening: In casual speech or writing, it might be a shortened version of a longer word. Without more information, it's impossible to know what it would stand for.
* On its own, possibly a grammatical particle: While less common, depending on dialect and extremely specific context, it *might* function as a particle indicating something like emphasis or a pause, but this is highly unlikely without more information.
To understand the meaning of "ku," you absolutely need the surrounding words and sentence. Providing more context will allow for a proper translation.