Bi-weekly

crosswatt said
It can actually mean both, but colloquial usage is pretty solidly into the every two weeks meaning.

Definition of biweekly

1: occurring twice a week

2: occurring every two weeks

http://www.merriam-webster.com/dictionary/biweekly

I liked this write up on it.

Usage note Expand

All words except biennial referring to periods of time and prefixed by bi-1are potentially ambiguous. Since bi- can be taken to mean either “twice each” or “every two,” a word like biweekly can be understood as “twice each week” or “every two weeks.” To avoid confusion, it is better to use the prefix semi- to mean “twice each”

So, it can bean both, but it's better to use semi to mean twice each, so that means it leaves bi-weekly to mean every 2 weeks.