Indiscriminately means in a random or careless way. If your teacher graded indiscriminately, she'd assign As and Ds haphazardly, without even considering her students' work.
This adverb is great for describing action that's taken in a completely unsystematic way. One child puts away his toys carefully, sorting blocks into one basket and stuffed animals into another. His sister, on the other hand, indiscriminately tosses all her toys into one large box. When you discriminate, you recognize the difference between things; act indiscriminately, and you pay no attention to these distinctions. An alternate meaning is "without judgment."