1. Lengthwise.

Nuttall's Standard dictionary of the English language By Nuttall, P.Austin

• longwave,
• longas,
• langwags,
• longways,
• lenthways,
• kongways,
• pongways,
• oongways,
• lingways,
• lkngways,
• llngways,
• longwayz,
• liongways,
• lonways,
• longwys,
• longway,
• longwayss,
• longweys,
• longwaise,
• longweise

• longest,
• longish,
• longwise,
• longs,
• longacre,
• long-ago,
• long whist,
• long ago.

The adjective form of the word "longways" is "longwise".

The plural form of the word "longways" is "longways".

The singular form of the word "longways" is "longway".