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ZEBRA MUSSEL A small freshwater mollusk that was accidentally introduced to North American waters via ballast water from a transoceanic vessel. The zebra mussel has had significant negative economic and ecological effects: It clogs water intake pipes and attaches to and fouls boat hulls, dock pilings and other objects.

ZENITH - The point of the celestial sphere which is directly overhead

ZEPHYR - A warm, pleasant breeze named after the mythical Greek god of wishful thinking, false hopes, and unreliable forecasts.

ZULU TIME - GMT- Greenwich Meridian Time, also known as Universal Time