smoking car vs smoking compartment

smoking car and smoking compartment both are nouns.

Word	Noun	Adjective	Verb	Adverb
smoking car	Yes	No	No	No
smoking compartment	Yes	No	No	No

As nouns, smoking car and smoking compartment are synonyms defined as:

smoking car and smoking compartment: a passenger car for passengers who wish to smoke

Other synonyms of smoking car include smoker, smoking carriage.

smoking car (noun)	smoking compartment (noun)
a passenger car for passengers who wish to smoke	a passenger car for passengers who wish to smoke