Def is a parameter that describes the DEF of a card.
Acceptable forms:
Def:300 ---exactly 300 DEF
Def:>300 ---greater than 300 DEF
Def:>=300 --greater than or equal to 300 DEF
Def:<300 ---less than 300 DEF
Def:<=300 ---less than or equal to 300 DEF
Def!:300 ----NOT 300 DEF
Spell and Trap cards (except Trap Monsters, etc.) will always test False for any of the above forms.