What does "seaplane" mean?

Any aircraft capable of taking off from, and alighting on the surface of water.

What is a synonym for "seaplane"?

Common synonyms include: aeroboat, aeroplane, airlift, airplane, amphibian, balloon.

/ˈsiˌpleɪn/ noun

noun ·Uncommon ·Advanced level

Noun

1
Any aircraft capable of taking off from, and alighting on the surface of water.
2
an airplane that can land on or take off from water wordnet

Verb

"We have a yacht, two helicopters, and a seaplane."

From sea + plane. Supposedly coined by Winston Churchill.