Meanings

impulse conduction system (of the heart)

deep brain stimulation

business-stimulating measures

extremism

flat-out run

extremely

irritability (of an organ, etc.)

heightened tension

radical Islamism

extreme weight gain

candidly revealing (secrets)

extremely crowded

melanocyte-stimulating hormone

being terribly grateful

I am terribly grateful

extremely expensive

major disaster (that necessitates economic support to its victims)

battleground state (in US politics)

extremely difficult

extremely low