Warning, this verb may not exist. Conjugation is given as example.
Affirmation
Simple form
I could enthusiasm you could enthusiasm he could enthusiasm we could enthusiasm you could enthusiasm they could enthusiasm
V-ing form
I could be enthusiasming you could be enthusiasming he could be enthusiasming we could be enthusiasming you could be enthusiasming they could be enthusiasming
Perfect
I could have enthusiasmed you could have enthusiasmed he could have enthusiasmed we could have enthusiasmed you could have enthusiasmed they could have enthusiasmed
V-ing perfect
I could have been enthusiasming you could have been enthusiasming he could have been enthusiasming we could have been enthusiasming you could have been enthusiasming they could have been enthusiasming
Negation
Simple form
I couldn't enthusiasm you couldn't enthusiasm he couldn't enthusiasm we couldn't enthusiasm you couldn't enthusiasm they couldn't enthusiasm
V-ing form
I couldn't be enthusiasming you couldn't be enthusiasming he couldn't be enthusiasming we couldn't be enthusiasming you couldn't be enthusiasming they couldn't be enthusiasming
Perfect
I couldn't have enthusiasmed you couldn't have enthusiasmed he couldn't have enthusiasmed we couldn't have enthusiasmed you couldn't have enthusiasmed they couldn't have enthusiasmed
V-ing perfect
I couldn't have been enthusiasming you couldn't have been enthusiasming he couldn't have been enthusiasming we couldn't have been enthusiasming you couldn't have been enthusiasming they couldn't have been enthusiasming
Interrogative form
Simple form
could I enthusiasm? could you enthusiasm? could he enthusiasm? could we enthusiasm? could you enthusiasm? could they enthusiasm?
V-ing form
could I be enthusiasming? could you be enthusiasming? could he be enthusiasming? could we be enthusiasming? could you be enthusiasming? could they be enthusiasming?
Perfect
could I have enthusiasmed? could you have enthusiasmed? could he have enthusiasmed? could we have enthusiasmed? could you have enthusiasmed? could they have enthusiasmed?
V-ing perfect
could I have been enthusiasming? could you have been enthusiasming? could he have been enthusiasming? could we have been enthusiasming? could you have been enthusiasming? could they have been enthusiasming?
Interro-negative form
Simple form
couldn't I enthusiasm? couldn't you enthusiasm? couldn't he enthusiasm? couldn't we enthusiasm? couldn't you enthusiasm? couldn't they enthusiasm?
V-ing form
couldn't I be enthusiasming? couldn't you be enthusiasming? couldn't he be enthusiasming? couldn't we be enthusiasming? couldn't you be enthusiasming? couldn't they be enthusiasming?
Perfect
couldn't I have enthusiasmed? couldn't you have enthusiasmed? couldn't he have enthusiasmed? couldn't we have enthusiasmed? couldn't you have enthusiasmed? couldn't they have enthusiasmed?
V-ing perfect
couldn't I have been enthusiasming? couldn't you have been enthusiasming? couldn't he have been enthusiasming? couldn't we have been enthusiasming? couldn't you have been enthusiasming? couldn't they have been enthusiasming?