What defines an Angel?

As we enter the Christmas season (I know Thanksgiving isn't past yet but I think this subject is appropriate) we think of the story of Christ's birth.  This story is full of angels bringing "glad tidings of great joy".  Often we think of Angels as this kind, those from the other side of the veil, but more often than not Angels are everyday people in our everyday lives.     
I believe an Angel is anyone who does anything to brighten someone elses day.  Often we don't think of simple things we do as "Angelic" or out of the ordinary but someone else does.  We don't know what impact a small act of love can do for someone in need.
Also being an angel doesn't mean you have to do something; sometimes being an Angel simply means being there, showing others we truly care and that they are more important than any "thing" in our lives.  I believe if we follow the advice from President Monson in this Mormon Message "What Matters Most" we can be Angels to those we meet.  
We need to let the Light of Christ shine through us by lifting up those that really need it.  As you go about your way think "What can I do to be an Angel to the people around me?"