The Defeated block is located in the exceptions drawer of the Blawx toolbox.
The Defeated block is used to query or state whether a conclusion reached according to a given section of the rules is defeated by another conclusion. Note that a conclusion need not defeasibly hold to be defeated. The defeated block only states that if the defeated conclusion would otherwise have held, it would be defeated. Not that it actually held and was defeated.
If you want to know if something actually held and was defeated, you need to check both the "according to" and "defeated" blocks using the same section and conclusion.
The Defeated block is a statement block which can be stacked with other statements. It accepts an input value which is a section selector or a variable, and an internal statement stack, which should be a single statement block, which is the conclusion that may or may not be defeated.
Generally, you don't need to use the defeated block in your code. Instead of making statements about defeating explicitly, it is easier to use the "overrules" block. Instead of asking questions about defeats, it is easier to ask whether the conclusion is true, or whether there is no evidence that it is true. If something is not true because it is defeated, that fact will appear in the explanations.
The main use of the defeated block is for troubleshooting problems with defeasibility in your rules.
The defeated block will only have an effect on rules and conclusions where the attributed rule block has been set "subject to exceptions", or in unattributed rules where it is being checked explicitly.