Is it permissible to suffice with wiping over the head when performing ghusl (ritual bath) after janabah (state of ritual impurity requiring ghusl) due to pain? And what is the meaning of the word "wird"?

If it is medically or experientially proven that washing the head with water during ghusl (ritual bath) causes harm, it is permissible to forgo it and suffice with wiping [the head]. Wird is the allotted portion or known measure of Qur’an, remembrance (dhikr), and prayer that a person habitually recites.