1. BROW — four letters
Trace BROW from 1 at row 4, column 1; 2 at row 3, column 1; 3 at row 2, column 1; 4 at row 1, column 1. Reading those cells in order gives B → R → O → W, with each letter immediately above the previous one.
All three moves go up, so the path stays within one column and makes no turns. It spans four rows, forms one straight segment, and visits four edge cells, including one corner. Both its starting and ending cells have two open orthogonal neighbors. After this word, four cells are assigned and 26 remain.