Wave height

From Glossary of Meteorology

wave height

In simple terms, the vertical distance between a wave crest and the preceding or following wave trough.

However, in a random sea, a variety of interpretations are possible. A commonly used definition is the so-called zero-upcrossing wave height, which is the range of elevations (difference between highest crest and lowest trough) between two successive upcrossings of the mean water level.
See wave frequency, wave length, wave period.