形容詞 ineffable:

1. defying expression or description
   同義詞：indefinable, indescribable, unspeakable, untellable, unutterable
2. too sacred to be uttered
   同義詞：unnameable, unspeakable, unutterable

1. The ineffable name of the Deity.
   神的名字是忌諱說的

in.ef.fa.ble

adj.（形容詞）
Incapable of being expressed; indescribable or unutterable.See Synonyms at unspeakable
不可言喻的：難以表達的；難以描敘的參見 unspeakable
Not to be uttered; taboo:
避諱的：不能說的；禁忌的：
例句：
the ineffable name of the Deity.
神的名字是忌諱說的

來源：
Middle English
中古英語
from Old French
源自 古法語
from Latin ineff3bilis
源自 拉丁語 ineff3bilis
in- [not] * see in-
in- [不] *參見 in-
eff3bilis [utterable] from eff3ro [to utter] ex- [ex-] f3ro [to speak] * see bh3- 2
eff3bilis [可說出的] 源自 eff3ro [說] ex- [前綴，表示.發(fā)出.] f3ro [說] *參見 bh3- 2

【引伸】
inef.fabil.ity 或
inef.fableness
n.（名詞）
inef.fably
adv.（副詞）