The "formal" term is motor terminal housing (Section 430.12) but motor terminal box or junction box are probably more common and perfectly acceptable.
You also failed to mention whether the motor was required to be explosionproof. Simply because it is explosionproof does not necessarily require it to be sealed in Division 2. Most three-phase motors in Division 2 are not required to be explosionproof and most single-phase motors in Division 2 are required to be.
Most explosionproof motors have a factory seal installed between the motor terminal housing and the main motor enclosure. Such motors will have a marking on the terminal housing stating it is factory sealed or something similar. The 2 inch entry seal applies only to Division 1.
Robert B. Alexander, P.E.
"I know that you believe you understand what you think the NEC says, but I am not sure you realize that what you read is not what it means." (Corollary to Charlie's Rule)
Answers based on 2014 NEC unless otherwise noted.