Mass. Gen. Laws ch. 186 § 23
"Co-tenant", a person who shares the legal obligation to pay rent or use and occupancy for the premises with a tenant and who occupies the premises.
"Domestic violence", the occurrence of 1 or more of the following acts between family or member of a household:
"Housing subsidy provider", a local housing authority, agency or other entity providing or administering a federal or state rental subsidy within the commonwealth under applicable law.
"Member of the household", a person residing with a tenant or co-tenant as an authorized occupant of the premises. In the case of an application for housing, such term shall include a person identified by the applicant as a proposed household member who would be living with the applicant in the premises.
"Owner", as defined in 105 C.M.R. 410.020.
"Qualified third party", a police officer, as defined by section 1 of chapter 90C, law enforcement professional including, but not limited to, a district attorney, assistant district attorney, a victim-witness advocate, probation or parole officer; an employee of the Victims Services Unit of the department of criminal justice information services; an application assistant in the address confidentiality program of the state secretary under section 2 of chapter 9A; a licensed medical care provider; an employee of the department of children and families or the department of transitional assistance charged with providing direct service to clients, or a manager or designated domestic violence or abuse advocate within either department; an active licensed social worker; a licensed mental health professional; a sexual assault counselor as defined in section 20J of chapter 233; or a domestic violence victims' counselor as defined in section 20K of said chapter 233.
"Quitting date", the date that a tenant or co-tenant surrenders such person's interest in the premises; provided further, that such date shall be determined as: (i) if the tenant or co-tenant has vacated the premises, the date notice is given to the owner of the intent to abandon the premises and not to return; or (ii) if the tenant or co-tenant has not vacated the premises, either (A) the date the tenant or co-tenant intends to vacate the premises or (B) the actual date that the tenant or co-tenant has vacated after providing such notice.
"Rape", as set forth in sections 22, 22A, 22B, 22C, 23, 23A, 23B, 24 or 24B of chapter 265 or sections 2, 3 or 17 of chapter 272.
"Sexual assault", as set forth in sections 13B, 13B, 13B, 13F, 13H or 13K of chapter 265 or section 35A of chapter 272.
"Stalking", stalking as set forth in section 43 of chapter 265 or criminal harassment as set forth in sections 43 or 43A of chapter 265.
"Tenant", (i) a person who has entered into an oral or written lease or rental agreement with the owner or (ii) a person who remains on the premises after such person's tenancy has terminated or after the expiration of such person's lease.
Mass. Gen. Laws ch. 186, § 23