patchy

The witness could only provide a patchy description of the suspect due to the heavy fog.

(Chinese) 由于大雾，证人只能对嫌疑人提供一个模糊且不完整的描述。

His knowledge of French grammar is rather patchy, though he speaks the language quite fluently.

(Chinese) 尽管他的法语说得很流利，但他对法语语法的了解却很不全面。