Atmospheric Pressure: The weight of a column of air on the earth's surface.

Barometer: Instrument for measuring atmospheric pressure.

Front: Boundary between two air masses. Could be cold, warm, or occluded. 

Hail: Frozen moisture formed by large cumulonimbus clouds.

Humidity: The amount of water vapor in the air measured using a hygrometer.

Meteorologist: A person who studies and predicts the weather.

Rain is measured by:
    Trace of precipitation: Less than 0.01 inches
    Measurable rain: 0.01 inches or more

Sleet: Partially frozen drizzle. Stings when it hits the skin.

The National Weather Service offers a very good list but it may not be applicable in all areas of the country.

Do you know what all these words mean? Test yourself