In Interet forum, someone responded to my post by saying: "I smell a field day". What does this actually mean?

Answer 1

To have a field day means to have no restrictions upon your actions, so if you're about to smell one there's lots of opportunity ahead.

Answer 2

Don't know the topic of conversation that it pertains to but it sounds like what they mean is that 'smells like a field day' is actually referring to being hogwild. For instance, all of your co-workers are esoterically sending hints your way about your retirement party. 'Smells like they are going to have a field day' with it.