Platyno (πλατύνω) means to make broad, to widen, to enlarge, or to open wide. It is the verbal form of platys (G4116, broad). In the NT it is used both literally — of Pharisees who broaden their phylacteries for show — and figuratively — of the heart being enlarged or opened wide in love and affection.
Jesus uses platyno in Matthew 23:5 to expose the Pharisees' hypocrisy: "They make their phylacteries wide" — enlarging the leather Scripture boxes worn on the arm and forehead to appear more devout. This is religion as performance art. In contrast, Paul uses the same word redemptively in 2 Corinthians 6:11-13, where he says "Our heart is opened wide to you... open wide your hearts also." Here platyno describes the generous, vulnerable expansion of the heart toward others in love. The word thus captures a profound biblical tension: the same "widening" can serve either vanity or love. God calls His people to enlarge their hearts (as in Psalm 119:32, "I run in the path of your commands, for you have broadened my understanding") rather than their outward religious displays.