Python in a Tie was an early nickname for a stable Python release that would be maintained for a reasonable period of time (18 months), without any (major, incompatible) feature additions, but regular bugfix releases.
Originally, this referred to 2.2, which was supposed to meet that promise. Now, the same no-new-features promise applies to any major python release, and they are all expected to be maintained for at least about 18 months from initial release.