curvilinearcur‧vi‧lin‧e‧ar /ˌkɜːvɪˈlɪniə $ ˌkɜːrvəˈlɪniər/ adjective formal 
having curved lines or a curved shape: 
curvilinear patterns
having curved lines or a curved shape: curvilinear patterns- underwent
- underwhelm
- underworld
- underwrite
- underwriter
- Underwriters' Laboratories
- undeserved
- undesirable
- undetected
- undeterred
- undeveloped
- undid
- undies
- undifferentiated
- undignified
- undiluted
- undiminished
- undischarged
- undisclosed
- undiscriminating
- undisguised
- undismayed
- undisputed
- undisturbed
- undivided