An ornate tent.
"The emperor rested under an elaborate pavilion decorated with intricate gold embroidery and silk curtains."
To furnish with a pavilion.
"The garden was paved and furnished with a pavilion to provide shelter from the sun."
In plain English: There is no verb form of pavilion; it is only used as a noun to describe an open-sided building or structure, often found at fairs or gardens.
"The new convention center features an open-air pavilion where guests can enjoy lunch under the stars."
The word "pavilion" entered English from Middle English, originally describing a tent that resembled the wings of a butterfly or moth. This connection between the structure's shape and insects is why the term shares roots with words for butterflies in French and Latin.