ef ‧ fu ‧ sion /ɪˈfjuːʒ ə n/ BrE AmE noun [uncountable and countable]
[ Date: 1400-1500 ; Language: French ; Origin: Latin effundere 'to pour out' ]
1 . technical a liquid or gas that flows out of something, or the act of flowing out:
a massive effusion of poisonous gas
2 . formal an uncontrolled expression of strong good feelings:
He greeted the guests with effusion.