A test tube baby was conceived by artificial means, by introducing the sperm and egg to each other outside the body. The zygote is then implanted into the future mother's womb.
Test tube babies are NOT born in test tubes. Not yet, anyway.
1. A child conceived via artificial insemination using a test tube. 2. Any such person who as an adult makes consistently poor decisions or otherwise acts foolishly. 3 A complete fuckin' idiot.
Somebody who was conceived in a test tube using sub-standard materials and poor quality control resulting in retardedness and stupid behaviour in their adult life.