1.Definition: having no known beginning and presumably no end

"Time is endless"

Related Adjective(s):dateless, sempiternal

2.Definition: having the ends united so as to form a continuous whole

"An endless chain"

3.Definition: infinitely great in number

"Endless waves"

4.Definition: tiresomely long; seemingly without end

"Endless debates", "An endless conversation"

Related Adjective(s):eternal, interminable