Marine forecasts contain a number of terms which are used to convey specific meanings.

Gale warnings

Gale		Winds of at least Beaufort force 8 (34-40 knots) or gusts reaching 43-51 knots
Severe gale		Winds of force 9 (41-47 knots) or gusts reaching 52-60 knots
Storm		Winds of force 10 (48-55 knots) or gusts reaching 61-68 knots
Violent storm		Winds of force 11 (56-63 knots) or gusts of 69 knots or more
Hurricane force		Winds of force 12 (64 knots or more)

Note: The term used is 'hurricane force'; the term 'hurricane' on its own means a true tropical cyclone, not experienced in British waters.

Imminent		Expected within six hours of time of issue
Soon		Expected within six to 12 hours of time of issue
Later		Expected more than 12 hours from time of issue

Visibility

Very poor		Visibility less than 1,000 metres
Poor		Visibility between 1,000 metres and 2 nautical miles
Moderate		Visibility between 2 and 5 nautical miles
Good		Visibility more than 5 nautical miles

Movement of pressure systems

Slowly		Moving at less than 15 knots
Steadily		Moving at 15 to 25 knots
Rather quickly		Moving at 25 to 35 knots
Rapidly		Moving at 35 to 45 knots
Very rapidly		Moving at more than 45 knots

Pressure tendency in station reports

Rising (or falling) more slowly		Pressure rising (or falling) at a progressively slower rate through the preceding three hours
Rising (or falling) slowly		Pressure change of 0.1 to 1.5 hPa in the preceding three hours
Rising (or falling)		Pressure change of 1.6 to 3.5 hPa in the preceding three hours
Rising (or falling) quickly		Pressure change of 3.6 to 6.0 hPa in the preceding three hours
Rising (or falling) v. rapidly		Pressure change of more than 6.0 hPa in the preceding three hours
Now rising (or falling)		Pressure has been falling (rising) or steady in the preceding three hours, but at the time of observation was definitely rising (falling)

Note: For those more familiar with the millibar, 1 hPa = 1 mb

Wind

Wind direction		Indicates the direction from which the wind is blowing
Becoming cyclonic		Indicates that there will be considerable change in wind direction across the path of a depression within the forecast area
Veering		The changing of the wind direction clockwise, e.g. SW to W
Backing		The changing of the wind in the opposite direction to veering (anticlockwise), e.g. SE to NE

Sea state

Smooth		Wave height less than 0.5 m
Slight		Wave height of 0.5 to 1.25 m
Moderate		Wave height of 1.25 to 2.5 m
Rough		Wave height of 2.5 to 4.0 m
Very rough		Wave height of 4.0 to 6.0 m
High		Wave height of 6.0 to 9.0 m
Very high		Wave height of 9.0 to 14.0 m
Phenomenal		Wave height more than 14.0 m