What is a "liturgical abuse"?

I am confused by the term “liturgical abuse”. I think it probably is due to the fact that something can be “illicit” without being “invalid”. Could you explain what would be considered liturgical abuse?

Thank you.

A liturgical abuse is an intentional non-permitted deviation from the liturgical norms in force by the Church. Some such deviations are more severe than others but, while all are illicit, not all result in something (e.g. the consecration) being invalid. For explanations of many common liturgical abuses see Redemtionis Sacramentum.

Recommended reading: Mass Confusion

DISCLAIMER: The views and opinions expressed in these forums do not necessarily reflect those of Catholic Answers. For official apologetics resources please visit www.catholic.com.