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 could not enthusiasm you could not enthusiasm he could not enthusiasm we could not enthusiasm you could not enthusiasm they could not enthusiasm
V-ing form
I could not be enthusiasming you could not be enthusiasming he could not be enthusiasming we could not be enthusiasming you could not be enthusiasming they could not be enthusiasming
Perfect
I could not have enthusiasmed you could not have enthusiasmed he could not have enthusiasmed we could not have enthusiasmed you could not have enthusiasmed they could not have enthusiasmed
V-ing perfect
I could not have been enthusiasming you could not have been enthusiasming he could not have been enthusiasming we could not have been enthusiasming you could not have been enthusiasming they could not 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
could I not enthusiasm? could you not enthusiasm? could he not enthusiasm? could we not enthusiasm? could you not enthusiasm? could they not enthusiasm?
V-ing form
could I not be enthusiasming? could you not be enthusiasming? could he not be enthusiasming? could we not be enthusiasming? could you not be enthusiasming? could they not be enthusiasming?
Perfect
could I not have enthusiasmed? could you not have enthusiasmed? could he not have enthusiasmed? could we not have enthusiasmed? could you not have enthusiasmed? could they not have enthusiasmed?
V-ing perfect
could I not have been enthusiasming? could you not have been enthusiasming? could he not have been enthusiasming? could we not have been enthusiasming? could you not have been enthusiasming? could they not have been enthusiasming?