Tailgate and Tail gate

Tailgate noun - A gate at the rear of a vehicle; can be lowered for loading.

Tail gate and tailgate are semantically related. In some cases you can replace phrase "Tail gate" with "Tailgate", this terms are similar.

Tail gate noun - A gate downstream from a lock or canal that is used to control the flow of water at the lower end.

Tailgate and tail gate are semantically related. You can use "Tailgate" instead the phrase "Tail gate" as a noun or a verb.