Christian observance of the final meal that Jesus observed with his disciples. It is usually observed with the Sacrament of Holy Communion.
(or Maundy Thursday): Commemorates the institution of the Lord's Supper/the Eucharist by Jesus prior to his arrest and execution. "Maundy" is derived from the Latin text of John 13:34, in which Jesus gives a mandatum novum ("new commandment"). The date observed by Protestants and Roman Catholics differs from the date observed by Orthodox Christians. (Christianity)
the Thursday before Easter; commemorates the Last Supper
In English usage, this has always meant the Feast of the Ascension (the fortieth day after Easter Day). (In continental or Roman usage, "Holy Thursday" means the Thursday in Holy Week, or Maundy Thursday.)
Holy Thursday is a poem by William Blake, from his book of poems Songs of Innocence. There is a poem called Holy Thursday in Songs of Innocence, and is the polar opposite to this song, which does not question the obvious differences in class, despite being in a Church which determines all men to be equal.
Holy Thursday was published in William Blake's "Songs of Experience" in 1794. This poem, unlike its contemporary in "Songs of Innocence", focuses more on society as a whole than the Holy Thursday ceremony.