toのつかない不定詞を原形不定詞と言う。

。

An infinitive without 'to' is called a bare infinitive.

Literal

'to' [subject-が] not-attached infinitive [object-を] base-form-infinitive [quotative-と] call.

A metalinguistic sentence explaining English grammar in Japanese — the kind found in Japanese English-language textbooks. 不定詞 (infinitive) and 原形 (base form) are grammatical terminology. The relative clause toのつかない modifies 不定詞. ~と言う defines a technical term.