That is to say

Say Say, v. t. [imp. & p. p. {Said} (s[e^]d), contracted from sayed; p. pr. & vb. n. {Saying}.] [OE. seggen, seyen, siggen, sayen, sayn, AS. secgan; akin to OS. seggian, D. zeggen, LG. seggen, OHG. sag[=e]n, G. sagen, Icel. segja, Sw. s["a]ga, Dan. sige, Lith. sakyti; cf. OL. insece tell, relate, Gr. 'e`nnepe (for 'en-sepe), 'e`spete. Cf. {Saga}, {Saw} a saying.] 1. To utter or express in words; to tell; to speak; to declare; as, he said many wise things. [1913 Webster]

Arise, and say how thou camest here. --Shak. [1913 Webster]

2. To repeat; to rehearse; to recite; to pronounce; as, to say a lesson. [1913 Webster]

Of my instruction hast thou nothing bated In what thou hadst to say? --Shak. [1913 Webster]

After which shall be said or sung the following hymn. --Bk. of Com. Prayer. [1913 Webster]

3. To announce as a decision or opinion; to state positively; to assert; hence, to form an opinion upon; to be sure about; to be determined in mind as to. [1913 Webster]

But what it is, hard is to say. --Milton. [1913 Webster]

4. To mention or suggest as an estimate, hypothesis, or approximation; hence, to suppose; -- in the imperative, followed sometimes by the subjunctive; as, he had, say fifty thousand dollars; the fox had run, say ten miles. [1913 Webster]

Say, for nonpayment that the debt should double, Is twenty hundred kisses such a trouble? --Shak. [1913 Webster]

{It is said}, or {They say}, it is commonly reported; it is rumored; people assert or maintain.

{That is to say}, that is; in other words; otherwise. [1913 Webster]