Reiner \re(i)-ner\ as a boy's name is a variant of Ragnar (Old Norse) and Rainer (Old German), and the meaning of Reiner is "judgment warrior; deciding warrior".

The baby name Reiner sounds like Regner and Reinier. Other similar baby names are Heiner, Einer, Gainer, Joiner, Kenner, Miner, Meinor, Rayner, Rainier, Reinart, Rainor, Raines, Raine, Rainger, Renier, Rene, Renne, Rider, River, Riker, Werner and Verner.