Obsolete?

I subscribed to an online OED word-a-day compendium, but today's word confused me:

Seven Sisters. [See also SISTER n.] 

    1. The Pleiades. Obs.

Obsolete?  I've always called the Pleiades the Seven Sisters (largely because I keep forgetting how to spell 'Pleiades').  Wikipedia lists the epithet, so it can't be completely out of use. 

The Pleiades are a small cluster of stars by Taurus.  Starting from Orion, follow the line made by the three stars of the belt on the upwards diagonal.  You should come to a reddish star (Aldebaran), which marks the upper-left corner of a V-shaped constellation (Taurus).  Just to the right of the V are the Pleiades.

What does everyone else call them? < edit > And where were you raised? < /edit >

In Japanese, they're known as Subaru, and the car emblem depicts the star cluster.