Pleonazo (πλεονάζω) means to be more than enough, to abound, to increase, to multiply, or to have in excess. It conveys the idea of overflowing abundance — going beyond what is merely sufficient to a state of superabundance.
Paul uses pleonazo to make one of the most radical declarations in Scripture: Romans 5:20 — 'Where sin increased, grace increased all the more.' No matter how sin multiplies, God's grace super-abounds beyond it. This is not a license to sin (Romans 6:1-2) but a declaration of the surpassing power of grace. In 1 Thessalonians 3:12, Paul prays that love would increase and overflow. In 2 Peter 1:8, possessing godly qualities in increasing measure keeps believers from being ineffective. The theological pattern is clear: in God's economy, what He gives always overflows, exceeds, and multiplies beyond our capacity to exhaust it.