A reply to an invitation.

(intransitive) To reply to an invitation.

(computing) Initialism of resource reservation protocol. / (cognition) Initialism of rapid serial visual presentation.

(restaurants, events) To reserve a place

Initialism of Royal Shakespeare Company. / Initialism of Royal Society of Chemistry.

Initialism of reticle shape correction.

Initialism of range safety officer. / Initialism of registered sex offender.

(Internet) Initialism of Rich Site Summary / Really Simple Syndication (“mechanism to follow updates on other websites such as news, music, blogs, etc.”).

(aerospace) Initialism of reusable spaceship. / (astronautics) Initialism of range safety system. / (statistics) Initialism of residual sum of squares.

(military) Initialism of regimental sergeant major. / (business) Initialism of regional sales manager.