antiphon

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A devotional composition sung responsively as part of a liturgy.
2. n. A short liturgical text chanted or sung responsively preceding or following a psalm, psalm verse, or canticle.
3. n. Such a text formerly used as a response but now rendered independently.
4. n. A response; a reply: "It would be truer . . . to see [conservation] as an antiphon to the modernization of the 1950s and 1960s” ( Raphael Samuel).

Century Dictionary and Cyclopedia

1. n. A psalm, hymn, or prayer sung responsively or by alternation of two choirs, as in the English cathedral service.
2. n. In the liturgy or mass of both the Eastern and Western churches, as well as in the day-hours and other offices, a series of verses from the Psalms or other parts of Scripture, either in their original sequence or combined from various passages, sung as a prelude or conclusion to some part of the service. It is sometimes especially limited to the verse sung before or after the psalms of the office, the tones of which are determined by the musical mode, according to the Gregorian chant, of their respective antiphons.
3. n. A scriptural passage or original composition sung as an independent part of the service, and set to more elaborate music; an anthem.
4. n. An echo or a response.

Wiktionary

1. n. A devotional piece of music sung responsively.
2. n. A response or reply.

GNU Webster's 1913

1. n. A musical response; alternate singing or chanting. See antiphony, and antiphone.
2. n. A verse said before and after the psalms.

WordNet 3.0

1. n. a verse or song to be chanted or sung in response