Definition of "300th" []

• The ordinal number of three hundred in counting order (adjective)

WordNet. Princeton University. 2010.

• "Oooooh, I'll be doing this in a few posts, to celeberate my '300th' post which is coming up ..."
• ""The 300th is a great opportunity for a lot of people to speak glowingly about 'Boomer' because he really deserves it."
• "A nationwide amnesty in honor of the 300th anniversary of the Romanov dynasty allowed Gorky to return to Russia in 1913, however, he found himself now at odds with the growing Communist party over his endorsement of the Bolsheviks."