acrostic acrostic /ˈækrɒstɪk/

noun

1. Verse in which certain letters such as the first in each line form a word or message  ( acrostic )
   verse in which certain letters such as the first in each line form a word or message
   
2. A puzzle where you fill a square grid with words reading the same down as across  ( acrostic , word square )
   a puzzle where you fill a square grid with words reading the same down as across