intersecond

Etymology
From. A recent coinage; see usage notes.

Adjective

 * 1)  Between the members of the second pair of specified things (such as premolars or molars).

Usage notes
The adjectives interfirst and intersecond in reference to teeth (premolars or molars) are rarely used nonstandard forms born of editorial errors. They arise from compound constructions such as /inter + first molar + distance/ (the distance between the in a given dental arch) that undergo a copyeditorial error in which a general rule to remove unnecessary hyphens from prefixes that don't need them is misapplied to a term where multiple hyphens or an en dash should have been used: either inter-first-molar distance (two hyphens) or inter–first molar distance (one en dash).