The term 'Tube Traveler' refers to a person who travels by underground train. The two crossword solutions for this term are 'EGG' and 'OVUM'. An EGG is a reproductive cell produced by a female organism, while an OVUM is the female reproductive cell that is released from the ovary and fertilized by a sperm cell. Both of these terms are related to the concept of tube travel, as they both refer to the process of reproduction.