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