Passive form of the verb آم
(Quoting Hans Wehr): آم ama i: آم من زوجته to lose one's wife, become or be a widower, آمت من زوجها to lose one's husband, become or be a widow

--------------------------------------------------
Note added at 1 hr (2008-11-12 21:23:38 GMT)
--------------------------------------------------

There's a منذ missing here though. I found it here:

قالت: أم العوام، أوتمْتُ منذ أعوام، أما ورب العباد، لتفترقُنَّ في البلاد، ثم ضربت بعصاها الأرض، فأثارت بها الرمل، وقالت: أطيلي إيابهمِ، وأنْفِرِي ركابهم، ...
www.ahlalhdeeth.com/vb/attachment.php?attachmentid=4657&d=1...

--------------------------------------------------
Note added at 1 hr (2008-11-12 21:30:29 GMT)
--------------------------------------------------

I've found several versions saying أرملت منذ أعوام online, which confirms that it means "widowed" (أرملة = widow).

--------------------------------------------------
Note added at 1 hr (2008-11-12 21:32:08 GMT)
--------------------------------------------------

There's also a version saying أيمت and another أويمت rather than أوتمت. I'm too tired to think about passive forms of double weak verbs!! But my feeling is that أويمت would be the correct form if آم is the verb.