Formal:
* Underdressed: This implies that the person is not appropriately dressed for the occasion.
* Incompletely dressed: This simply states that the person is not fully clothed.
* Partially clothed: This is a more neutral term that simply describes the state of being dressed.
* Disheveled: This suggests that the person's clothing is messy or unkempt.
Informal:
* Half-dressed: This implies that the person is only partially clothed.
* Scruffy: This suggests that the person is messy and unkempt, including their clothing.
* Sloppy: This implies that the person is careless in their appearance, including their clothing.
* In a state of undress: This is a more formal way of saying that the person is not fully dressed.
* In a tizzy: This implies that the person is in a hurry and has not had time to dress properly.
Humorous:
* Looking like a rumpled mess: This is a playful way of describing someone who is not well-dressed.
* In a state of semi-nudity: This is a humorous way of describing someone who is only partially clothed.
The best word to use will depend on the context and the tone you want to convey.