。
Meiji lost to Keio by a score of 5-3.
Literal
Meiji [topic-は] 5-to-3 [possessive-の] score [with-で] Keio [to-に] lost.
Refers to Meiji University and Keio University, two of the oldest private universities in Japan. Their rivalry is particularly fierce in baseball (within the Tokyo Big6) and rugby. 敗れる ('to be defeated/lose') takes に for the winner — 'lose to X.' 対 reads たい here, marking a score or contest: '5対3' = '5 to 3.'