“3rd” (third) means:

• The ordinal form of 3, showing position in a sequence.
  • Example: He finished 3rd in the race = he came in position number three.
• It can also refer to:
  • The 3rd day of a month (e.g., July 3rd)
  • The third item, rank, or place in any ordered list

In short, it means number three in order or rank.