The term tacit programming describes code written without dfns or tradfns. Its opposite is named explicit programming because these defined functions refer explicitly to their arguments. In tacit programming, arguments are left unmentioned.
sum ← {+⌿⍵} ⍝ Explicit sum ← +⌿ ⍝ Tacit
Fully tacit programming requires operators and syntax which can manipulate the flow of arguments.
square ← {⍵×⍵} ⍝ Explicit square ← ×⍨ ⍝ Tacit
The explicit square
's definition makes it clear that it is intended for use with only one argument, but the tacit code can be used with two!