say it: END-luh-slee
endlessly is an adverb meaning "continuing forever without end". It carries 4 recorded senses.
with unflagging resolve
“dance inspires him ceaselessly to strive higher and higher toward the shining pinnacle of perfection that is the goal of every artiste”
(spatial sense) seeming to have no bounds
“the Nubian desert stretched out before them endlessly”
all the time; seemingly without stopping
“a theological student with whom I argued interminably”
“her nagging went on endlessly”
Definitions, synonyms and semantic relations for endlessly come from Princeton University’s WordNet. The pronunciation comes from the CMU Pronouncing Dictionary. Commonness is measured against a corpus of everyday English. Full sources and licences.