Why is a 3.3 foot wave considered a tsunami?

It dosnt matter if the wave is only 3.3 feet tall its that tsunamis, typically, are really long if you have a 3.3 foot wall of water that stretch for a mile when it comes the distance it can travel and the , and the thing about tsunamis is they often come in

****It dosnt matter if the wave is only 3.3 feet tall its that tsunamis, typically, are really long if you have a 3.3 foot wall of water that stretchs back into the ocean for a mile when it comes to shore the distance it can travel is very large , and the thing about tsunamis is they often come in groups of really powerfull sets.****

I would guess that maybe the 1 meter wave is the wave on the ocean, typically they grow in size before they hit the coast.

Did you see footage of the Indian Ocean tsunami? Tsunamis aren't giant single monster waves, they are more like huge surges of water that can raise sea level in an area and cause major flooding. Earthquakes (and other under-water events) can cause tsunamis when they displace water, in the case of an earthquake the sea-bed shifts. The displaced water rushes in or out of the area where the shift was and causes a big wave out at sea that when it reaches the shore is essentially a huge gush of water.

It's called a tsunami if the source of the wave is geologic rather than wind or current driven. Tsunamis may be caused by earthquakes, landslides, volcanic activity, meteorite impacts, etc. Tsunamis may, especially in the open ocean, not create a visible wave at all, but rather an invisible "hump" or change in sea level. As Annie said, the danger of tsunamis is not the height of the waves, usually, but rather the immense energy stored in the surface gravity wave rippling through the ocean. As the tsunami reaches shore, the depth of the ocean decreases, and the same energy must pass through a rapidly decreasing volume of water, creating ever higher waves far more powerful than wind-driven waves. If the natural resonating period of the harbor is a multiple of the wave period of the tsunami, a harmonic effect results in a "seiche" or standing wave, which can exceed 60 ft. high. Tsunami waves are in essence temporary changes in sea level. Frequently, the tsunami wave (an increase in sea level) is preceded by a decrease in sea level, exposing usually covered areas. If you are on the beach and suddenly the shoreline goes out 30-40 feet, you are possibly a few minutes or seconds from a world of hurt. Some geologists believe the volcanic explosion of the Greek island Santorini around 1600 B.C. may have caused a seiche in the Red Sea resulting in the shallow Red Sea receding to the seabed, shortly followed by a large seiche wave, historically recorded as Moses' crossing of the Red Sea.

So the 3.3 feet measurement would be the amount the sea level would rise? Or the height of the wave before it reaches the shore?

It was caused by an underwater earthquake or volcanic eruption…therefore considered a tsunami.