Sec Form 3 Filing - Hamood Samuel A @ Definitive Healthcare Corp. - 2021-09-15

FORM 3 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person Hamood Samuel A 2. Issuer Name and Ticker or Trading Symbol Definitive Healthcare Corp. [ DH] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) X __ Director _____ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) C/O DEFINITIVE HEALTHCARE CORP., 550 COCHITUATE RD 3. Date of Earliest Transaction (MM/DD/YY) 09/15/2021 (Street) FRAMINGHAM, MA01701 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) __ X __ Form filed by One Reporting Person _____ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Class A common stock 37,037 D

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares LLC Units of AIDH Management Holdings, LLC ( 1 ) ( 2 ) ( 1 )( 2 ) ( 1 )( 2 ) Class A common stock 310,078 I By trust

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Hamood Samuel A C/O DEFINITIVE HEALTHCARE CORP. 550 COCHITUATE RD FRAMINGHAM, MA01701 X Signatures By: /s/ David Samuels, as attorney-in-fact 09/15/2021 Signature of Reporting Person Date

Explanation of Responses:

( 1 )AIDH Management Holdings, LLC ("Management Holdings") is a special purpose investment vehicle through which interests in AIDH Topco, LLC are indirectly owned. Certain unvested awards vest in equal installments on each of the first, second and third anniversaries of the Issuer's initial public offering, and the remainder of the unvested awards continue to vest pursuant to a four-year annual vesting schedule. Once vested the Reporting Person may exchange LLC Units of Management Holdings for LLC Units of AIDH Topco, LLC on a one-for-one basis, which are exchanged for shares of Class A common stock of the Issuer on a one-for-one basis, subject to certain exceptions, conditions and adjustments. The LLC Units of Management Holdings have no expiration date. ( 2 )(Continued from Footnote 1) At the time of any such exchange, an equal number of shares of Class B Common Stock of the Issuer held by the Reporting Person, which have no economic value and entitle holders thereof to one vote per share on all matters on which stockholders of the Issuer are entitled to vote generally, are cancelled.

Remarks: Exhibit 24 - Power of Attorney

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

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