According to the Vermont website:
A Resident is an individual that is domiciled in Vermont or maintains a permanent home, and is physically present in the state for 183 days or more.
A Nonresident is an individual that does not qualify as a resident or part-year resident during the tax year.
A Part-Year Resident is an individual that qualifies as a resident for only part of the year.
What if I am a resident and my spouse is not?
If one spouse is a resident and the other is not, you can elect to file a married filing separate return. To do this within your account, you can file the federal return and wait for the return to be accepted. Then, change the filing status for the primary taxpayer and file a separate return for the first spouse. The second spouse will need to create a new account and file the separate state return in that account (if required to file).
For more information: