quadrilateral
equadilateral
oblong; such as an oval or rectangle
Excommunicate is a 13 letter word. It begins and ends with the letter e.
Base of a triangle or breadth of a rectangle
In the absence of a definition, I'll provide one. What is a 13 letter word for vertical? Answer: perpendicular
Boardinghouse and brainstorming are 13 letter words. The 3rd letter is the letter a.
What is another word for rectangle?
oblong.
Some 13 letter words that start with the letter a:abbreviationsabnormalitiesacceptabilityaccessibilityaccommodationaccreditationacquaintancesacupuncturistadministratoradmissibilityadvertisementaffordabilityalgebraicallyalternativelyanniversariesannouncementsanticipationsapplicabilityappropriationapproximationarchitecturalassassinationassignabilityastonishinglyattainabilityattentivenessauthenticallyauthoritativeauthorization
Correspondent
The Welsh word for 'rectangle' is petryal.
perpendicular