Tatpurusa
In Sanskrit grammar a tatpuruṣa compound is a dependent determinative compound, i.e. a compound XY meaning a type of Y which is related to X in a way corresponding to one of the grammatical cases of X.
There are many tatpuruṣas (one for each noun case, and a few others besides); in a tatpuruṣa, one component is related to another. For example, "boathouse" is a dative compound, a house on a boat. It would be called a caturthī-tatpuruṣa (caturthī refers to the fourth case — that is, the dative). The most frequent kind is the genitive tatpuruṣa. Examples are:-
jaya-prepsu = "victory-desiring". (accusative)
varṣa-bhogya = "year - going to be enjoyed" = "to be enjoyed for a year" (adjective). (accusative)
deva-datta = "god-given" = "given by the gods". (instrumental)
viṣṇu-bali = "Vishnu-offering" = "offering to Vishnu". (dative)
svarga-patita = "heaven-fallen" = "fallen from heaven". (ablative)
tat-puruṣa = "that-man" in the sense of "that person's man". (genitive)
vyāghra-buddhi = "tiger-thought" = "thought of it being a tiger". (genitive)