From the Sefer Nishmas Avraham Siman [182][1] 

וכן שמעתי מהגרש״ז אויערבאך זצ״ל
לגבי בחור שצמחו לו שערות בין שתי
גבות עיניו שזה נקרא מום ומותר לו
להסירם: Uni brow is called a blemish and it can be removed.


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The Shulchan Aruch ([182:1][2]) holds like the Rambam (Avodas Kochavim 12:9; [translation][3] available) that one can remove other hair from the body with scissors  except for the armpits and bais ha'erva. However there is a Mordichai that holds it is assur unless it causes the person tzar(pain),but the Shulchan Aruch doesn't bring that opinion down.

See Nazir [58b][4] for the discussion of this topic.


  [1]: http://www.hebrewbooks.org/pdfpager.aspx?req=51474&st=&pgnum=162
  [2]: http://www.hebrewbooks.org/pdfpager.aspx?req=40533&st=&pgnum=425
  [3]: http://www.chabad.org/library/article_cdo/aid/912371/jewish/Avodah-Kochavim-Chapter-Twelve.htm
  [4]: http://www.hebrewbooks.org/shas.aspx?mesechta=17&daf=58b&format=pdf