Is there a name for this hair pattern?

Solution 1:

It appears to me that there is no popular term for that particular stage before reaching complete baldness (see: Male Pattern Baldness). Like jxh said in a comment:

The patterns are typically numbered. E.g., Type IV or Type V, depending on who is writing the chart. The charts are typically laid out from when balding starts to when balding is near complete.

Meanwhile the internet users may call that stage as "M-shape" or "U-shape". But probably more common is "horseshoe hairline". For example, see this one from Google Books / A.D.A.M. Illustrated Family Health Guide: