"overall strengthening" means the improvement or enhancement of something as a whole. It means making something better in every aspect or making it stronger overall. Full definition
With the expected changes on the policy front and overall strengthening of the macro-economic scenario, the industry is poised to enhance its value proposition across the product and service spectrum. (policybazaar.com)
Whether that's just me having faith in the squad or the overall strengthening of the team — in sometimes imperceptible ways, admittedly — is an open question. (liverpooloffside.sbnation.com)
Colostrum, a relatively new product on the market, is noted for reversing Candidiasis, while providing an overall strengthening of the immune system. (appliedhealth.com)