by

immensements

Apart from the possibility of being a French loanword, I think Larkin has another great nonce word in his poem “Sad Steps”:

There’s something laughable about this,

The way the moon dashes through clouds that blow
Loosely as cannon-smoke to stand apart
(Stone-coloured light sharpening the roofs below)

High and preposterous and separate—
Lozenge of love! Medallion of art!
O wolves of memory! Immensements! …