1) Amplification 2) Back up 3) Becoming stronger 4) Building up 5) Buttressing 6) Corroboration 7) Defence 8) Enrichment 9) Escalation 10) Fortification 11) Fortifying 12) Growth 13) Increase 14) Invigorating 15) Reinforcement 16) Rise 17) Spiralling 18) Support 19) Underpinning 1) Bracing 2) Buildup 3) Concentration 4) Corroborant 5) Fortifying 6) Intensification 7) Invigorating 8) Nourishing 
• (p. pr. & vb. n.) of Strengthen • (a.) That strengthens; giving or increasing strength.
Strength'en·ing adjective That strengthens; giving or increasing strength. -- 
Is a hedging or risk management term used to describe the relative gain of value between the underlying market and the hedge vehicle. It suggests that the cash or spot commodity or market is becoming more valuable relative to the futures or forward as defined by the basis. 
[n] - becoming stronger 2. [n] - the act of increasing the strength of something
noun the act of increasing the strength of something
The addition of a carriage to a train, usually on an ad-hoc basis, for a specific service!