The term "epitaph" refers to an inscription on a tombstone, commemorating the person buried there. Here's the analysis of the options:
- Eulogy: Refers to a speech or writing in praise of someone, typically delivered at a funeral or memorial service, but it is not inscribed on a tomb.
- Epitaph: Refers specifically to the inscription on a tombstone, often summarizing the deceased person's life or achievements.
- Epigraph: Refers to a short quotation or inscription at the beginning of a book or chapter, not related to tombstones.
- Epigram: Refers to a short, witty, or satirical poem or remark, unrelated to inscriptions on tombs.
Therefore, the correct answer is "epitaph".
\[
\boxed{2. \, epitaph}
\]