Demi in French means half of a whole and Sec in this particular case means dry. The direct translation means ‘half dry’ but this can be interpreted in two ways. Is it half dry on the sweet side or half dry on the dry side?
In this case it is sweeter than Sec but not as sweet as the sweetest Champagne style referred to as ‘Doux’.
To the unseasoned wine drinker, Demi-Sec will still taste very sweet because it typically has around 32-50 grams of sugar per Litre (35-50g/L).