Learn how to say Diagonalisable correctly in English with this tutorial pronunciation video.

Oxford dictionary definition of the word diagonal:

adjective

(of a straight line) joining two opposite corners of a square, rectangle, or other straight-sided shape.

(of a line) straight and at an angle; slanting:

a tie with diagonal stripes

noun

a straight line joining two opposite corners of a square, rectangle, or other straight-sided shape.

Mathematics the set of elements of a matrix that lie on a line joining two opposite corners.

a slanting straight line:

the bars of light made diagonals across the entrance

tiles can be laid on the diagonal

Chess a slanting row of squares whose colour is the same.

Origin:

mid 16th century: from Latin diagonalis, from Greek diagōnios ‘from angle to angle’, from dia ‘through’ + gōnia ‘angle’