From Longman Dictionary of Contemporary Englishfathomlessfath‧om‧less /ˈfæðəmləs/ adjective literary DEEPimpossible to measure or understand the fathomless depths of the sea
Examples from the Corpus
fathomless• The grin vanished like magic, her whole body stiffening in antipathy as her eyes locked with fathomless brown ones.• The fifteen girls across the bar turned their eyes on him with identical expressions of bland, fathomless contempt.• Who would sleep with need as strong as his, with loneliness of such fathomless depth?• She lay limply in his arms, those cloudy, fathomless eyes gazing up into his.• For a long moment all she could do was stare back at him, his dark fathomless eyes holding her in thrall.• Refugee camps came into being, people were uprooted, the economy lagged behind and you created fathomless sadness. 