Smearing is a term used in rock climbing.
It is the practice of using the sole of a shoe against a flat rock face. Smearing can be one of the most insecure and technical techniques used in climbing, requiring a combination of leg/ankle tension, foot placement, and good balance. It is frequently used on slabs, and in other situations with sparse and/or sloping footholds.
Smearing can be one of the techniques with which novice climbers are least confident - however, it is crucial to learn how to smear properly at an early stage, as it tends to help in the development of a more elegant and less tiring style of climbing whereby a greater amount of weight is placed on the feet, and less on the arms and hands.