Antonyms for Tense (opposite meaning)
WordNet sense 1 (without strain or anxiety):
relaxedWordNet sense 2 (pronounced with muscles of the tongue and jaw relatively relaxed (e.g., the vowel sound in `bet')):
laxWordNet sense 3 (become less tense, rest, or take one's ease):
relaxWordNet sense 4 (cause to feel relaxed):
unstrainFrom the ODE community, based on WordNetadd/edit