"Flight in icing conditions prohibited", so says the Flight Manual.
I read this, and luckily so does my company as "conditions conducive to icing" i.e. 0 degrees, visible moisture, viz below 1000m etc. If such conditions are forcast on your route you should avoid it. By penitrating the area you are in breach of the limitation section in the flight manual.
The word "conditions".
As a verb: To make dependent on a condition or conditions.
As a noun: a circumstance indispensable to some result; prerequisite; that on which something else is contingent.
Both come up with the same answer. a number of prerequisites occuring together to give in our case Icing.
There is a subtle difference between flight in icing conditions and flight in icing.
The first, your going to get it, the second, you've got it.