Chambers 20th Century Dictionary(0.00 / 0 votes)Rate this definition: 1  Rock. rok, n. a large mass of stone: (geol.) a natural deposit of sand, earth, or clay: that which has the firmness of a rock, foundation, support, defence: (Scot.) a distaff: a hard sweetmeat.âv.t. to throw stones at.âns.
Since B-vitamins can be somewhat activating, it is best to take a multivitamin in the morning or afternoon. Minerals such as calcium and magnesium that serve as natural muscle relaxants can be taken in the evening to ensure a good nightâs sleep.
If you really need one, the best time is between 2 p.m. and 3 p.m. Your blood sugar levels start to dip after lunch, and itâs early enough that it wonât mess with your bedtime. But donât overdo it -- 20 minutes is enough to make you more alert and put you in a better mood.