<entry id="2280547" stat="A" corpus="jmdict" type="jmdict">
<ent_corp type="jmdict">jmdict</ent_corp>
<ent_seq>2522580</ent_seq>
<k_ele>
<keb>凹多角形</keb>
</k_ele>
<r_ele>
<reb>おうたかくけい</reb>
</r_ele>
<sense>
<pos>&n;</pos>
<xref type="see" seq="2522590">凸多角形</xref>
<field>&geom;</field>
<gloss>concave polygon</gloss>
<gloss>non-convex polygon</gloss>
</sense>
<info>
<audit time="2009-11-14 00:00:00" stat="A">
<upd_detl>Entry created</upd_detl>
</audit>
<audit time="2023-10-17 06:22:50" stat="A" unap="true">
<upd_name>Brian Krznarich</upd_name>
<upd_email>...address hidden...</upd_email>
<upd_detl>Google search will confirm this formulation is quite common.

Can't speak to "reentrant" myself.</upd_detl>
<upd_refs>Wikipedia 
A simple polygon that is not convex is called concave,[1] non-convex[2] or reentrant.[3]</upd_refs>
<upd_diff>@@ -12,0 +13 @@
+&lt;field&gt;&amp;math;&lt;/field&gt;
@@ -13,0 +15 @@
+&lt;gloss&gt;non-convex polygon&lt;/gloss&gt;</upd_diff>
</audit>
<audit time="2023-10-17 11:04:07" stat="A">
<upd_uid>jwb</upd_uid>
<upd_name>Jim Breen</upd_name>
<upd_email>...address hidden...</upd_email>
</audit>
<audit time="2023-10-18 19:20:17" stat="A">
<upd_uid>robin1354</upd_uid>
<upd_name>Robin Scott</upd_name>
<upd_email>...address hidden...</upd_email>
<upd_diff>@@ -13 +13 @@
-&lt;field&gt;&amp;math;&lt;/field&gt;
+&lt;field&gt;&amp;geom;&lt;/field&gt;</upd_diff>
</audit>
</info>
</entry>