Suppose you have a multi-module gradle project with nested structure. Eg: module A depends on B, B depends on C and so on. And you want to exclude module C from A.
So, here's how you can exclude a 'transitive' module prj-C from prj-B at Project A
build.gradle -- at Project A
dependencies {
    implementation ( project(':prj-B')){   //note the parenthesis 
        exclude group: 'com.gt', module: 'prj-C'
    }
    //other dependencies
}
Bonus:
If you want to exclude a transitive dependency (not the module) you can do the following:
dependencies {
    implementation 'com.gt:libraryA'{
        exclude group: 'com.gt', name : 'libararyB'
    }
    //other dependencies
}