What does chrismus mean in Latin?

chrismus, a noun, means “Eucharist; Christogram, chrismon”.

What is the genitive of chrismus?

The genitive singular is chrismī. chrismus is masculine, second declension.

In classical Latin, [ˈkʰrɪs.mʊs]; in ecclesiastical (church) Latin, [ˈkriz.mus].

noun · masculinesecond declension

chrismus m (genitive chrismī)

Classical[ˈkʰrɪs.mʊs]Ecclesiastical[ˈkriz.mus]

chrismōs pl. acc.

masculineEucharist
Quot sunt inquit sacramenta Ecclesiae? Repsond. tribus. Et episcopus Quibus. Chrismus, baptismus, & missa pro defunctis.“How many,” [he] said, “are the sacraments of the Church?” [The other] responds: “Three [in number].” And the bishop [said], “Which [in number]?” “The Eucharist, Baptism, and Mass for the Dead.”1577, Gabriel de Barletta, Sermones, volume 1, page 114:
B[ishop]. Quot sunt septem Sacramenta? S[chollar]. Tribus, viz. Chrismus, Primus et Baptismus.Bishop: How many are the seven sacraments? Scholar: Three [in number], namely the Eucharist, the first and baptism.1814, Unknown, quoting John Tutchin, “Nugae. № XXVII”, in The European Magazine, and London Review, volume 65, page 194:
masculineChristogram, chrismon
Est vero Chrismon sive Chrismus, si eius originem spectes, nihil aliud, quam signum pietatis christianae, ac sigillatim inuocationis diuinae, vel etiam iurisiurandi taciti, quo quis se ad seruanda, quae promittebat, obligauit.1765, Johann Christoph Gatterer, Elementa artis diplomaticae universalis, page 145:

First attested in the 16th century in New Latin, from Middle Latin crismon.