adverb & adjective. Of, along, or in reference to the direction of the length; longitudinally.

In the direction of the length; in a longitudinal direction.

adjective. In the long direction of an oblong object.

adverb. In the long direction of an oblong object.

adverb. in the direction of the length

adjective. running or extending in the direction of the length of a thing

"He slid the knife in lengthwise beneath the skin and then ran a straight incision down the spine all the way to the tail, four feet distant."

crosswise  sideways  

axial  end-to-end  fore and aft  linear  longitudinal  

atom-laser  gill-like  inch-wide  keycard  knifelike  

along  along  at full length  at length  endlong