1. (n.) The insertion of a day, or other portion of time, in a calendar.

2. (n.) The insertion or introduction of anything among others, as the insertion of a phrase, line, or verse in a metrical composition; specif. (Geol.), the intrusion of a bed or layer between other layers.

a huis clos all apart askance askant askew aslant aslope asquint away awry back behind closed doors beside between the teeth broadside broadside on by crabwise discursion divagation downgrade downhill each edgeway edgeways edgewise episode excursion excursus glancingly in a whisper in an aside in camera in chambers in executive session in juxtaposition in privacy in private in private conference in privy in reserve infix injection insert insertion insinuation intercalation interjection interlineation interlocution interpolation introduction januis clausis laterad laterally monodrama monologue monology nearby nigh obiter dictum obliquely on its side on one side on the beam on the side out of earshot parenthesis per per capita privately privily remark right and left round side remark sideling sidelong sideward sidewards sideway sideways sidewise sidling slant slantingly slantways slantwise slaunchways slopeways soliloquy solo sotto voce to one side to the side tossing-in wide apart wide away with bated breath