GG5: a sponger; a hanger-on 《pl. hangers-on》. ●あいつは親のすねかじりだ. He 「sponges [lives] on his parents.
脛齧り	469	2.0% - GG5 
スネ齧り	227	1.0%
すね齧り	82	0.4%
スネ噛り	23	0.1%
脛噛り	36	0.2%
すねかじり	16486	71.8%
スネかじり	4669	20.3%
脛かじり	978	4.3% - 中辞典 adding

Trimming. I think it's the person, not the act.

@@ -3,0 +4,3 @@
+<k_ele>
+<keb>脛かじり</keb>
+</k_ele>
@@ -11,0 +15 @@
+<ke_inf>&sK;</ke_inf>
@@ -14,0 +19 @@
+<ke_inf>&sK;</ke_inf>
@@ -17,0 +23 @@
+<ke_inf>&sK;</ke_inf>
@@ -21,8 +26,0 @@
-<re_restr>脛齧り</re_restr>
-<re_restr>すね齧り</re_restr>
-<re_restr>脛噛り</re_restr>
-</r_ele>
-<r_ele>
-<reb>スネかじり</reb>
-<re_restr>スネ齧り</re_restr>
-<re_restr>スネ噛り</re_restr>
@@ -33,3 +31,2 @@
-<gloss>sponging (e.g. off one's parents)</gloss>
-<gloss>sponger</gloss>
-<gloss>freeloading</gloss>
+<gloss>sponger (e.g. off one's parents)</gloss>
+<gloss>hanger-on</gloss>
@@ -37 +34 @@
-<gloss>leach</gloss>
+<gloss>leech</gloss>

See similar glosses:
居候 lodger who pays nothing for room and board; freeloader; sponger
たかり屋 freeloader; scrounger; sponger; mooch

https://eow.alc.co.jp/search?q=live+off+one's+parents
表現パターンlive [leech, mooch, sponge] off one's parents

I am spoiled and am freeloading off my parents.
https://www.reddit.com/r/TrueOffMyChest/comments/pgz54k/i_am_spoiled_and_am_freeloading_off_my_parents/

I'm Disgusting. How Do I Stop Leaching Off My Parents?
https://www.reddit.com/r/selfhelp/comments/17pf8eq/im_disgusting_how_do_i_stop_leaching_off_my/

Don't know if "sponger" is regional English.  It feels uncommon to me in AmE. I think I recognize it, but would have thought it dated if in the U.S. 

"leach" is the word my intuition came up with.  But freeloading  (from the related terms) seems quite good.

I'd be inclined to at least demote "sponging", unless it seems exceptionally natural to you all.  It's secondary on the other jmdict terms.

@@ -34,0 +35,3 @@
+<gloss>freeloading</gloss>
+<gloss>freeloader</gloss>
+<gloss>leach</gloss>

GG5: 脛噛り
Daijr: 脛齧り
G n-grams:
脛齧り	469
すねかじり	16486
スネかじり	4669
スネ齧り	227
脛噛り	36
スネ噛り	23
すね齧り	82
すね噛り	< 20

Could be split into senses.

@@ -6,0 +7,12 @@
+<k_ele>
+<keb>スネ齧り</keb>
+</k_ele>
+<k_ele>
+<keb>すね齧り</keb>
+</k_ele>
+<k_ele>
+<keb>スネ噛り</keb>
+</k_ele>
+<k_ele>
+<keb>脛噛り</keb>
+</k_ele>
@@ -8,0 +21,3 @@
+<re_restr>脛齧り</re_restr>
+<re_restr>すね齧り</re_restr>
+<re_restr>脛噛り</re_restr>
@@ -11,0 +27,2 @@
+<re_restr>スネ齧り</re_restr>
+<re_restr>スネ噛り</re_restr>

Seen in a gameo.

@@ -9,0 +10,3 @@
+<r_ele>
+<reb>スネかじり</reb>
+</r_ele>