During the 1980s nickels were churned out in mass quantities, with sub-par quality control, particularly at the Philadelphia mint. Dies were used so long they became worn, and the devices of the coins they produced look mushy. These are not errors but rather poorly struck coins from late state dies.
At first glance such nickels appear heavily circulated, but with closer examination one can see they were from late die state strikes. In the example from 1983 below, note the bumpy areas to the right of God and left of Liberty. Since those area look like the skin of a citrus fruit, they're often called "orange peel". Orange peel would be worn smooth on a heavily circulated coin, so its existence means an old die resulting in a poor strike. The reverse of this coin has large areas of orange peel.
The hair near Jefferson's ear often shows no detail, and the area can even be flat, not from wear but from the lack of a strike. This area is opposite the highest area on the reverse and thus experiences less die pressure relative to other places on the coin.
Lettering is often of uneven or soft clarity. In the example below, In and God are not too bad, but We is mushy soft. On the reverse Unum is fading into the background. With some practice you'll be able to distinguish a poor strike from honest circulation wear.
In a way these can make for an interesting variety for which to search. Mint state examples can be tough to find since they were less often saved because of the poor strike. I'll post more of the ones I've found from the 1980s.

