re·dou·ble 
/riˈdʌbəl/ verb
re·dou·bles; re·dou·bled; re·dou·bling /riˈdʌbəl/ verb : to greatly increase the size or amount of (something) [+ obj] ▪ They redoubled their efforts to finish the work on time. [no obj] ▪ Their efforts to finish the work redoubled as the deadline drew near.
