An underdog is a person or group in a competition, frequently in electoral politics, sports and creative works, who is popularly expected to lose. The party, team or individual expected to win is called the favourite or top dog. In the rare case where an underdog wins, the outcome is an upset. These terms are commonly used in sports betting. The use of the term is believed to have come from the job of plank making where the lower saw-pit worker was called the underdog as they were underneath the metal brackets (dogs) which held the log in place.

an underdog is one at a disadvantage or that is expected to lose

loser

it means with out any expectation

International football: Russia v Brazil. Russia is the underdog.