| Webster's Online Dictionary |
| Expressions | Domain | Definition | |
| Blue line | Census | A boundary that defined the extent of the area covered by the block canvassing operation, and later was included in the mailout/mailback and urban update/leave enumerations. Most mailing addresses inside the blue line use a house number and street name. (references) | |
| Blue line | Medicine | Bluish discoloration of the gums at the margin of the teeth seen in chronic lead poisoning (4). Source: European Union. (references) | |
Source: compiled by the editor from various references; see credits. | Top | ||