The short answer
A jacuzzi, whirlpool and jetted tub are the same thing in a hotel room: a bathtub with water jets that you fill for each use. A hot tub stays full and heated; in a room it is usually on a private deck or balcony. A soaking tub is deep but has no jets. A spa tub or spa bath can be either, so check for the word jets.
How often hotels use each word
Across the tub rooms on Tubroom: whirlpool tub 81.4%, jacuzzi tub 16.9%, hot tub 8.1%, 2-person tub 2.9%, soaking tub 2.4%, spa tub 2.0%, heart-shaped tub 0.7%. A room can carry more than one word, so these add to more than 100%.
Which ones count on Tubroom
We list a room when it has a jetted tub (jacuzzi, whirlpool, jetted, spa tub with jets) or its own hot tub. We leave out soaking tubs without jets, and any hot tub shared with other guests by the pool or gym.
Room size
Where hotels give the size, a jacuzzi room is a median 390 sq ft (middle half 325 to 500 sq ft). 4.6% of the rooms we list say the tub fits two. See hotels with a 2 person jacuzzi.