WordNet sense 1 (one of three equal parts of a divisible whole):

one-third, tierce

WordNet sense 2 (the third from the lowest forward ratio gear in the gear box of a motor vehicle):

third gear

WordNet sense 3 (the base that must be touched third by a base runner in baseball):

third base

WordNet sense 4 (coming next after the second and just before the fourth in position):

tertiary

WordNet sense 5 (being or denoting a numerical order in a series):

ordinal

WordNet sense 6 (constituting or comprising a part or fraction of a possible whole or entirety):

fractional

WordNet sense 7 (in the third place):

thirdly