Noun
antimins
(Christianity) A rectangular piece of linen or silk, usually decorated with religious emblems and inscriptions, and containing a small relic of a martyr.
A bishop bestows faculties (permission to minister within his diocese ) giving a priest chrism and an antimins ; he may withdraw faculties and demand the return of these items. Source: Internet
The antimins is a silk cloth, signed by the appropriate diocesan bishop, upon which the sanctification of the holy gifts takes place during each Divine Liturgy. Source: Internet
This means that most parishes or congregations, unless they have more than one officially signed antimins and multiple priests, can celebrate only one Eucharist per day, in order to express the catholicity of the church by avoiding "private masses". Source: Internet