n. — proprietary, Urban culture
someone who has volunteered their home as a refuge, particularly for neighbourhood children, in an emergency.
Type: 5. Frequency — A block parent is a volunteer who is part of a program to assist neighbourhood children and other local people in an emergency. Block parent is a registered trademark. The Block Parent program originated in the US and was active in some US cities as early as the 1950s. The program was first introduced to Canada in 1968 in London, Ontario. A national Block Parent committee was formed in 1983, and in 1986 the Block Parent Program of Canada was incorporated (see Block Parent reference). The nationalization of the program may explain the high prevalence of the term in Canada (see Chart 1). In the US, the programs often operate at local levels, and there is no national US program.
See also COD-2, s.v. "Block Parent", which is marked "esp. Cdn".
Images:

Chart 1: Internet Domain Search, 11 Sep. 2013